than pillars. As the narrator approaches the house, he first journeys over a causeway, symbolizing that he is the only connection between the Ushers and the outside world. They are otherwise isolated.

When the narrator is inside the house, he realizes that the walls are covered by dark draperies. The health of the siblings is failing, and these draperies symbolize the way death seems to press in on them from all sides.

It is also the case that the twins Madeline and Roderick are also symbolic in their nature.  For Poe, the story itself is about the duality of human nature and the struggle between the dualism of emotion/body and rationality/mind within the individual.  Roderick represents the human innate mental capacity as he is a character who is all mind in a weak and deteriorating body.  Roderick is constantly engaged in the intellectual; he engages almost entirely in reading, making music, and creating art.  Conversely, his doppleganger Madeline, is entirely a description of her body without reference to her mind.  Madeline is "the gradual wasting away of a person" and most notably a body/corpse in the end of the story.  The two are unable to survive without one another as demonstrated by Madeline's return from the tomb to reclaim her twin.  This symbolism suggests that the human body and mind struggle to exist within the same individual but are ultimately necessary to complete each person.  Moreover, denial of the body or the mind results in an untenable existence and the only way to achieve true harmony is to accept the necessity of both the mind and the body.  

You can actually start with the title of the story, which alludes to the absolute chaos that lurks within the mansion. This "broken" house is "falling" in every way. Genetically speaking, the Ushers clearly sound like they are the product of generations of inbreeding, or else generations of careless mating. They are a sickly clan, vulnerable, and weak. 

He suffered much from a morbid acuteness of the senses; the most insipid food was alone endurable; he could wear only garments of certain texture; the odours of all flowers were oppressive; his eyes were tortured by even a faint light; and there were but peculiar sounds, and these from stringed instruments, which did not inspire him with horror. 

The Ushers' penchant for isolation also places them in a somewhat supernatural realm where they exist with the world, but not "in" the same world as everyone. It is as if "the house of Usher" is the only niche where they can actually exist...and now, it can no longer resist it: it is falling apart. 

The house, as well as its resident, is described:

with an utter depression of soul which I can compare to no earthly sensation more properly than to the after-dream of the reveller upon opium--the bitter lapse into everyday life--the hideous dropping off of the veil

All of this is symbolic of the mental, spiritual, and physical state of this rare family, which (as it is debated) could even represent a fragment of the narrator's own state of mind. As "a house", the "house of Usher" really encompasses the entire generation of Ushers. They are a dying race; they are disappearing and the house is falling from its foundation. 

The fissure (split) in the Usher mansion is another symbol. This represents the split of the twin personalities of the surviving Ushers, predicting the destruction of the family and the house.

Roderick's lyric, "The Haunted Palace", is another symbol in the book. It represents death and madness. His abstract painting is a "phantasmagoric" idea of the narrator and represents the "fantastic character" of his guitar playing.

The inability of Madeline to have children symbolizes the end of the Ushers. When Roderick dies, there will be no one to carry on the name.

According to Poe, the whole story is symbolic of the Apocalypse, the end of the world.

The narrator uses a metaphor to describe the "utter depression of soul" that he feels when he looks at the home and its environs. He compares this depression to "the after-dream of the reveller upon opium." A metaphor is a comparison of two unalike things where the speaker says that one thing is another. This comparison emphasized the deadening feeling he gets just by looking at the house. He also says that he felt an "iciness, a sinking, a sickening of the heart." This is another metaphor where the speaker compares the feeling of dread, of foreboding, to being cold.  His heart is not actually getting colder or sinking down.  

When the narrator describes the letter he received from his old friend, Roderick Usher, he describes the request for him to visit and "the apparent heart that went with his request . . . " This line employs a figure of speech called metonymy: when the writer replaces a detail associated with a thing for the thing itself. In this case, what the narrator means is that the request was made with so much feeling, and since we associate feelings with the heart (however erroneously), heart can replace feeling for emphasis and remain understandable. 

Throughout the short story "The Fall of the House of Usher," Edgar Allan Poe uses figurative language to describe the environment and events of the story as well as emphasize various characteristics of the home and its objects and tenants. Poe incorporates a literary device known as personification throughout the story.

Personification occurs when an inanimate object is given human attributes. While the unnamed narrator is commenting on the various activities that he participated in to cheer up Roderick Usher, Poe writes,

"We painted and read together, or I listened, as if in a dream, to the wild improvisations of his speaking guitar" (11).

The guitar is personified when it is given the human quality of speech. Poe also incorporates the literary device known as hyperbole throughout the short story. Hyperbole is an exaggeration that is used to add emphasis to whatever the narrator is addressing. When the unnamed narrator describes the mournful songs that Roderick sings, he says,

"His long improvised dirges will ring forever in my ears" (Poe 11).

Commenting that the dirges will "forever" play in his ears is hyperbole. The narrator is exaggerating the lasting impact that Roderick's mournful songs will have on him by stating that they will last "forever."

You might like to look at the ending for an excellent example of figurative langauge that Poe employs to help convey the horror and terrror in this excellent story. Let us remember that figurative language takes the form of comparing one thing to something else, either through use of a simile, a metaphor, or personification. As the narrator flees the house and turns back, note how a simile is used to describe the sound of the House of Usher as it, like its owners, meets its end:

...there was a long tumultuous shouting sound like the voice of a thousand waters--and the deep and dank tarn at my feet closed sullenly and silently over the fragments of the "House of Usher."

Note how the supernatural end of the mansion is stressed through the comparison of the sound it makes in its final moments to the "voice of a thousand waters." Hopefully this example will help you go back and spot and analyse other examples of figurative language in this excellent short story. What, for example, is suggested by the windows of the house being described as "eye-like" as the narrator first looks upon the House of Usher?

When assessing the conflict(s) in a story, it can be helpful to identify its climax, or the moment of the most tension in the text. It can also be a turning point of some kind. In this story, the climax takes place when Madeline Usher emerges from her tomb, still alive (though her brother and the narrator believed she was dead when they interred her) and covered in blood, looking wild and frightful. She approaches her brother and falls, dead, on top of his body. He falls to the floor underneath her and dies in this moment as well.

It's a strange moment that contains a weird intimacy, but these two people have always been close intimates, so to speak: they shared a womb (as twins), and they were also expected to continue the Usher line by having children together before Madeline grew sick. The narrator points out that there are no offshoots on the Usher family tree, and it is, perhaps, this pattern of mating with one's siblings that has caused the illnesses that have corrupted the physical and mental health of Roderick and his sister.

For this reason, I think it makes the most sense to identify the main conflict of the story as a character vs. character conflict (between Roderick and Madeline), but we might also consider the possibility of a character vs. society conflict (between Roderick and his family as a result of their strange and skewed values: keeping the bloodline intact, etc).

The central conflict that is present in Edgar Allan Poe's "The House of Usher" involves the unstable conditions of Roderick Usher.

In this Gothic thriller, Roderick Usher suffers from internal conflicts. These conflicts are composed of three components: his sensory sensitivity, his fears, and his anxiety. Although the terminology was unavailable to Poe in his time, Poe describes in Usher the psychological condition of hyperesthesia, which is an extreme sensory sensitivity. For instance, he is extremely affected by such things as light, sounds, smells, and tastes. This "constitutional and family evil" involves Roderick's suffering from "a morbid acuteness of the senses":

...the most insipid food was alone endurable; he could only wear garments of a certain texture; the colors of all flowers were unendurable; his eyes were tortured by even a faint light.

There are also sounds that seem "peculiar" to Roderick. Some of these sounds are made by stringed instruments, and their vibrating sounds cause Roderick to become fearful.

As his fear grows, Roderick becomes terrorized by his acute anxiety. Because of this anxiety, Roderick has frightening anticipations of going mad and dying. In fact, as the narrator makes efforts to relieve his friend's fears and melancholy by engaging in painting with him and by listening to Roderick's dirges and unusual interpretive renditions of the music of Von Weber, he perceives:

...a full consciousness on the part of Usher of the tottering of his lofty reason upon her throne. 

That is, Roderick Usher himself realizes that he is becoming mentally unstable. Usher's instability also becomes apparent as he tells the narrator that the old house itself is making odd sounds.

Roderick also suffers from hypochondria, thefear of illness.The Usher family has virtually wasted away, and only he and his sister remain. Roderick is especially worried about his sister's illness and the fact that if Madeline Usher dies, his only remaining relative will be gone. He is also probably anxious about his own health since she is his twin sister.

As he tries to cheer Usher by painting and reading with him, the narrator specifically alludes to hypochondria in his comments upon Roderick's painting:

...there arose out of the pure abstractions which the hypochondriac contrived to throw upon his canvas, an intensity of intolerable awe.

These unstable conditions of Roderick Usher contribute to the internal conflicts which develop the strange narrative and its horror in Poe's Gothic tale.

There are several conflicts in "The Fall of the House of Usher." First, there is the internal conflict that Roderick Usher is experiencing. He is losing his mind and his health, and he knows that his paranoia is growing. As the story progresses, Roderick is also struggling with the knowledge that he has essentially buried his sister alive, and he is waiting for her to emerge. This conflict between Roderick and Madeline is the main external struggle. Madeline's return is the end of both Roderick and Madeline, thus bringing the family Usher to an end.

These two conflicts are mirrored in the natural conflict seen in the short story. The weather is extremely significant in the story. As Roderick progressively loses the battle with himself and his sister, the weather progressively grows more and more severe, battering the already crumbling house. Just as Roderick loses his battle, and both he and Madeline die in the end, the house loses its conflict with the weather and literally falls. Poe effectively concludes with both the literal and figurative "houses" of Usher falling.

In a symbolic sense, the crumbling decay of the Usher home seems to represent the ever-crumbling home life suffered by the author. The unnamed narrator says of the house,

I looked upon the scene before me—upon the mere house, and the simple landscape features of the domain — upon the bleak walls—upon the vacant eye-like windows — upon a few rank sedges—and upon a few white trunks of decayed trees — with an utter depression of soul which I can compare to no earthly sensation more properly than to the after-dream of the reveller upon opium — the bitter lapse into every-day life — the hideous dropping off of the veil.

The house is in absolute decay and produces within the viewer a terrible sense of depression, hopelessness, and even confusion. This may bear some similarities to Poe's own life. Poe's father first abandoned his family, leaving Poe's mother all alone with three children. Then, by the time Poe was three, his mother died of tuberculosis while her very young son watched. After this, the Poe children were split up, and Edgar was sent to live with the family of his mother's good friend, Frances Allan; Poe loved Frances a great deal. However, she soon died of tuberculosis as well, leaving Poe alone with his foster father, a hard man who always thought Poe was an ungrateful burden. Poe's home life crumbled over and over again, and the crumbling of the literal house of the Ushers could be seen to symbolize this.

Further, the unnamed narrator of the story tells us "that the entire [Usher] family lay in the direct line of descent." In other words, then, the Usher family seems to have routinely practiced incest, and it is, perhaps for this reason that the Ushers suffer from such strange illnesses. Poe, in real life, married his cousin, Virginia, when she was only thirteen years old. He even referred to her as "sissy" as often as he referred to her as "wifey," appearing to combine several female roles into one and ascribing them all to Virginia. By all accounts, their relationship was loving, but she was a child and his relative, and this is quite troubling as well.

Poe certainly had a sad life. He was a typical struggling writer who even burned his furniture at one point to stay warm. He found success with the Raven but then lost his wife a year or so later. If Poe had the medical advancements of our day, i bet he would havebeen diagnnosed with paranoia and depression; both for which I think he self-medicated with alcohol.

The character of Usher is totallly paranoid as well as depressed and superstitious. Put all three of these mental illnesses in an old neglected and possessed house and the combination clearly leads to insanity.

Usher was lonely like Poe must have been. Usher's mind obsesses over circumstances he either cannot change or  is too despondent to address; possibly like Poe too.

In the end, a life like that isbound to crumble just like the house did.

I think that the climax is the night of the eight day, when they start to hear noises and when Madeline bursts into the room where he and Roderick are. The falling action is the ensuing struggle and when both Roderick and Madeline are dead. The resolution is when the narrator runs out of the house, and he then sees the house crumble.

However because of the way this story is structured, you could adjust it somewhat.

Falling action concludes and ties up a story after the climax has been reached. It is a point at which tension is released.

There is not much falling action in this Poe story, as the climax comes very near the end. In this climax, the bloody Madeline emerges from having clawed her way out of the crypt, and she and Roderick both die.

The falling action comes as the narrator flees the house. The house begins to fissure and collapse. The falling action is actually the house falling into the tarn, where, as the narrator watches, the:

deep and dank tarn at my feet closed sullenly and silently over the fragments of the "House of Usher."

The house of Usher in the last words of the story refers both the physical house itself and the house—or bloodline—of the Usher family, which died off for good when Roderick and his twin sister perished.

Without doubt, there has been much debate on the interpretation of Edgar Allan Poe's "The Fall of the House of Usher" as to whether it is a tale of natural or psychological forces acting together, supernatural forces acting, or symbolic forces acting out a sort of Apocalypse. Nevertheless, in each of these interpretations, the setting plays an important role. For, as a Dark Romantic, Poe most certainly perceives nature as a force. But, while the Romantics felt that nature was in unison with the human spirit, imbuing it with knowledge and leading man to the spiritual world, in his story, Poe apparently depicts nature much as Melville does in Moby Dick as Captain Ahab perceives it as an inscrutable malice. He informs his crew, "All visible objects, man, are but as pasteboard masks" that hide behind them "a reasoning mask," a force.

As the Dark Romantic, then, Poe skewers the Romantic idea of Nature as reflective of the soul's emotions and insights, and gives to Nature the role of destructive driving force, the inscrutable malice that permeates the home and minds of the Ushers. This fits Poe's idea of the Arabesque, a technique of repeating and louping bizarre traits. Thus, the narrator arrives at the Usher estate only to find the outside reflective of what transpires within. for, he immediately remarks upon the "insufferable gloom" that pervades his spirit as he approaches the "melancholy House of Usher":

I was forced to fall back upon the unsatisfactory conclusion that while, beyond doubt, there are combinations of very simple natural objects which have the power of thus affecting us, still the analysis of this power lies among considerations beyond our depth.

The narrator shudders as he gazes at the

remodeled and inverted images of the grey sedge, and the ghastly tree stems and the vacant and eyelike windows.

Later, after greeting the host of the decaying mansion, the narrator finds him in "perfect keeping" with the "character of the premises." Then, he alludes to the "equivocal appellation" of the House of Usher--

an appellation which seemed to include in the minds of the peasantry who used it both [the]family and [the] mansion.

Moreover, the mansion's atmosphere seems to the narrator to be connected by its decay and disease to the underworld. It is this force, then, that creates the fungi and decay outside as well as within the house the fissure in the walls that forms a zigzag from the roof to the wall, a fissure that widens as Roderick begins to break down. "An air of stern, deep and irredeemable gloom hung over and pervaded itself," the narrator observes. And, reflective of this gloom is the change in Roderick Usher because of a "family evil." Further, Roderick speaks to the narrator of a "sufferance of spirit" which is provoked by 

"...the physique of the gray walls and turrets, and of the dim tarn into which they all looked down...."

Indeed, Roderick Usher exists in a terrible and perverse connection with his surroundings, one which forms Poe's Arabesque of death for both Usher the family and the Usher mansion. Similarly, his twin Madeline suffers from a "settled apathy, a gradual wasting away of the person," reflective of the decay of the mansion and the surrounding area.

As the narrative continues, Roderick Usher expresses the belief that all things, living or non-living, are sentient. Thus, there is an interaction among them. He tells his friend that the waters and the walls have a atmosphere of their own. His books, the narrator observes, "in strict keeping of the phantasm" in keeping with the character of the phantasm. And, as Roderick falls prey to this interaction with his environment, his eye loses it luminous quality and assumes an empty and ghastly appearance not unlike the "vacant and eyelike" windows of the mansion first noted by the narrator in the exposition of the story. Later, when Roderick's sister dies he wanders through the house; opening the door, there is a tremendous whirlwind that sends inside vapors that "enshrouded the mansion"--a phrase mirrored by the "enshrouded figure of the lady Madeline Usher" who issues forth from her vault to embrace her brother in a death grip a final agonies for both. As they collapse in this terrible embrace, the fissure of the walls widens, and the "deep and dank tarn...closed sullenly...over the fragment of the "House of Usher." 

One element that characterizes American Gothic literature is the intersection of the rational and the irrational. The story's narrator is the voice of reason; he comes to the House of Usher because his old acquaintance has indicated that he's having some difficulties, and the narrator believes it is his duty to help. The narrator realizes that Roderick looks very weak and sickly, and he soon recognizes that events within the house are hard to reconcile with rational behavior. One is the return of Madeline Usher from what seems to him to be death, since he helps to entomb her.

Another element of gothicism is the confrontation of guilt. Roderick Usher knows that the incest that his family has long engaged in is problematic, yet it is apparent that he and his sister Madeline are heir to the behavior. It is possible that he entombs her to bring to an end the family's curse of inbreeding over which he apparently feels immense guilt.

Madness is a theme often explored in gothic literature, and Roderick Usher's mental state suggests that he has become seriously destabilized. It may be the genetic result of his ancestors' incest, it may be a result of the isolation in which he and his sister have been living, or it may be those things and other causes. Regardless, he suffers distorted thinking and sensations that he describes to the narrator. His senses, for example, are hyper-attuned to the point of pain.

Writers of Gothic narratives often employ the setting of the forbidding-looking or haunted house, and the physical structure of the House of Usher aligns with that idea. The narrator describes it as being surrounded by vegetation that he imagines to be sentient, and its windows are described as eyelike.

A final element of gothicism often involves death. The narrator assists Roderick in entombing his sister because he believes that she has died. She eventually claws her way out of the crypt and, in doing so, causes her brother's and her own death when she confronts him.

One of the important aspects of the house in this story is the way that it functions as such a vital symbol of Roderick and Madeline Usher themselves and how it is suggested that the house and the last Usher members are linked in some kind of mysterious bond that means that the death of the members of the House of Usher results in the destruction of the house. It is important to realise how Poe creates this supernatural link. Note how the house is described when the narrator finally reaches the gloomy and depressing scene that awaits him:

In this there was much that reminded me of the specious totality of old wood-work which has rotted for long years in some neglected vault, with no disturbance from the breath of the external air. 

We are presented with a house that is so incredibly old and ancient that it is slowly rotting and falling apart, just like Roderick and Madeline are clearly rotting and falling apart psychologically and healthwise. The death of these two characters results in the "death" of the house and the wiping out of any trace of the House of Usher on the earth. The Gothic importance of this setting is thus stressed through the link that is created between the house and Roderick and Madeline.

Certainly, Poe uses mood to great effect in the story, making word choices that convey the gloom and moroseness of the house and landscape.  Details about the "clouds [that] hung oppressively low" over the "singularly dreary tract of country" before the description of the "melancholy House of Usher" help us to feel the gloom and sadness—even the rankness of the house—as the story's rising action is just beginning.

The narrator compares the sight of the house to the soul's depression that accompanies the "after-dream of the reveller upon opium—the bitter lapse into every-day life—the hideous dropping off of the veil." Here he seems to compare—via metaphor—the feeling of seeing the House of Usher to the experience of coming close to death.  In addition to employing this comparison, these lines continue to contribute to the foreboding mood: nothing good can happen in this place.

Poe employs imagery when the narrator describes his second view of the house—from a hill above.  He has allowed his imagination to run away with him:

An atmosphere peculiar to [the mansion and grounds] and their immediate vicinity—an atmosphere which had no affinity with the air of heaven, but which had reeked up from the decayed trees, and the gray wall, and the silent tarn—a pestilent and mystic vapor, dull, sluggish, faintly discernible, and leaden-hued.

This visual and even somewhat olfactory description of the grayish, heavy, disease-like mist presents a vivid image that sets the scene and further contributes to the mood.

While there exist differing interpretations of Edgar Allan Poe's "The Fall of the House of Usher," certain aspects are undeniable.  One such aspect is that of the characteristic Dark Romanticism of the author.  Certainly, the forces of the natural world work against, or at least, mirror the forces working within the characters of Poe's narrative.  Thus, the Gothic aspect of the story prevails throughout the setting as well as within the character development.

With the double entendre of the title as a reinforcement of this parallelism, there is an effective suggestion of evil and madness, two themes which are evinced in Poe's story.  For instance, as the narrator approaches the house of the Usher family, he becomes aware of the atmosphere of dread and menace of the "insufferable gloom [that] pervaded [his] spirit."  Such details as the "decayed trees with an utter depression of soul," and the "iciness, a sickening sickness of the heart" that the narrator experiences parallel the decadence of the figurative family tree of Roderick and Madeline Usher, as well as the degeneration of the Usher family, which leads to the bizarre illnesses of the siblings.

Furthermore, as the mind and the body of Roderick and Madeline respectively deteriorate, so, too, does the mansion decay.  A fissure in the wall is observed, fungi develops on the stones of the exterior.  In Roderick his acute sensitivity to noises disturbs him excessively.  This "sentience of all vegetable things" mirrors this sensitivity of Roderick.  Likewise, Madeline's corpse in the coffin mirrors the face of her twin brother who possesses a "restrained hysteria in his whole demeanor."  As Roderick reads to his friend later on, Roderick starts, "Madman! I tell you that she now stands without the door!"  Thus, the madness and evil of the atmosphere and the happenings of the interior of the mansion, meet forces and join together for the horrifying end as Madeline returns from the coffin to take in her brother with an eerie and deadly embrace. Simultaneously, the fissure widens and the "mightly walls rush asunder," destroying all of the House of Usher; the double entendre of the two meanings for the "The House of Usher"--the mansion and the family--and the parallelism of evil with madness is complete.

Whenever you are asked this kind of question about a text the main thing to think about is what the concerns are of the text you are studying. However, it is slightly misleading to think that any text is built around one single theme. The vast majority of texts have a multiplicity of themes. Considering "The Fall of the House of Usher," therefore, I will talk about one of the themes which is madness, however you might want to analyses other themes such as the nature of evil as presented in this excellent tale.

When we think about insanity in this story it is clear that this theme emerges from the ever-more unstable condition of Roderick Usher who is suffering from an unspecified nervous condition which is very mysterious. The narrator describes him as "a bounden slave" and he is told that his condition is related strongly to the actual House of Usher that has already been described to us looking so grey and grim. Yet there is also a link between Roderick's illness and his sister's strange malady, that causes her to become cataleptic. Roderick, desperately, tries to use the narrator's company to engage in other activities to ease his malady, yet in spite of these efforts, his actions become more and more hysterical, and we as readers, just like the narrator, are left to wonder about what is behind these increasingly frenzied actions. It is a mark of Poe's excellence that the reason for this insanity always remains ambiguous (possible incestuous relationship or evil, vampiric possession?), yet we would be wrong to focus so strongly on the theme of evil in this story that we forget the questions it raises about the frenzied descent into the maelstrom of madness that we are presented with by Roderick Usher.

Hope this helps - you might want to re-read the story and think about what it says about evil now. Good luck!

Friendship is an important theme.  The narrator drops everything in order to answer his friend's plea to come "NOW".  He has a foreboding feeling as he approaches the house which is in a desheveled state...everything is crumbling, which leads us to the theme of morality.  The twins and the house are all connected.  The house's state of disrepair is a symbol for the moral, physical, and mental state of Roderick and his sister.  Illness is obvious in the two, and the house, which used to be a grand estate, has sunk along with them...alll the way into the ground upon the death of the last two Ushers.  So, it is a complete "Fall" of the house and the family whose name the house carries.

The house is then buried, just like Roderick when the house falls in on him.  He is, essentially, buried alive as his sister was.  If you believe that she was buried alive...was she?  Or was it a product of Roderick's madness and insanity?  Of course, the narrator swore he heard the scratching sounds as well, but did he temporarily succumb to madness while in the house?   

The theme of incest has often been tossed around as the exact relationship of the twins, Roderick and Madeline Usher, isn't made clear.  She and he seem to be more than just brother and sister, they are intertwined, connected in ways that may just be the way of twins, but could be more.

Much of the element of the grotesque in this Gothic tale lies in the incest of the Usher "race" that

had put forth, at no period, any enduring branch;...the entire family lay in the direct line of descent, and had always, with very trifling and very temporary variation, so lain.

It would seem, then, that the family had done as many aristocratic families in England so often did:  They married cousins (which was not then illegal) and, thereby, made the bloodline so thin--incestuous--that many died or possessed genetic deficiences causing epilepsy and conditions such as Madeline and Roderick possess.  The brother and sister are almost the same person because of this thin bloodline, their gene pool is so small that they share many of the same traits and have this bizarre affinity to one another. (the grotesque) 

Like twins who share the same genetic code, Roderick senses what is going on with his sister:  He knows that she is not really dead when the physician pronounces her so.  His art reflects Roderick's knowledge of family history; the lyrics express the demise of a once great "House"/family:

And travelers now within that valley,/Through the red-litten [bloodline] windows, see/Vast forms that move fantastically/To a discordant melody...A hideous throng rush out forever

The "vast forms that move fantastically" is reflective of the grotesque.  Poe used the term "arabesque" for his technique of repeating and louping bizarre traits as he does incest with art and madness.

Setting, as your question identifies, is absolutely crucial to this excellent short story, as the setting helps create the foreboding atmosphere of imminent doom and terror that pervades the entire text. Note how even in the first paragraph, as the narrator comes upon the House of Usher, the mood of the setting is clearly established:

I had been passing alone, on horseback, through a singularly dreary tract of country; and at length found myself, as the shades of the evening drew on, within view of the melancholy House of Usher. I know not how it was - but, with the first glimpse of the building, a sense of insufferable gloom pervaded my spirit... I looked upon the scene before me - upon the mere house, and the simple landscape features of the domain - upon the bleak walls - upon the vacant eye-like windows - upon a few rank sedges - and upon a few white trunks of decayed trees - with an utter depression of soul which I can compare to no earthly sensation more properly than to the after-dream of the reveller upon opium - the bitter lapse into everyday life - the hideous dropping off of the veil.

This description continues, establishing the profound and horrific impact that seeing the House of Usher has upon the narrator. Note how specific words of description such as "melancholy," "mere," "vacant," "rank," and "decayed" help reinforce this atmosphere of a stagnant setting that strikes terror into the narrator's soul.

Absolutely vital to note is how this feeling of horror is repeated as the narrator sees his old friend again and then sees his sister. There is evidently a link between the heirs of the House of Usher and the house itself, that joins them in their fate. Note how Roderick and Madeline and the House itself all perish together, indicating that the curse that is upon the House of Usher will bring it down completely. It is this link that is influenced by the setting, as the effect of the House on the narrator is mirrored by his meeting with the actual heirs of the House.

The question "What is the situation that revolves around the characters?" is a fairly standard literary question that aims at directing a student to a specific aspect of literary criticism, namely, how the situations of the plot affect and involve the characters. Firstly, examine the definition of situation as stated by Random House Dictionary (on Dictionary.com), which may be a condition, a case, or a plight as well as a state of affairs or a combination of circumstances. Therefore one paraphrase of what the question is asking can be, "What is the state of affairs or plight that revolves around the characters?"

Secondly, the phrase revolves around is actually a metaphorical figure of speech, seeing that plights and states of affairs don't actually move in circles around characters. This metaphorical figure of speech is in fact an idiom, which is defined as an expression that has a nonliteral meaning that can be understood based upon cultural agreement of meaning (e.g., "You're a Babe Ruth!"); in other words, what revolves around means in America is not likely to be what it means in Korea or elsewhere. [Which, incidentally, is why idioms give learners of a second language so much difficulty: such learners don't have the cultural background necessary for understanding idioms, tied as they are to cultural meaning.]

According to McGraw-Hill Dictionary of American Idioms and Phrasal Verbs, the culturally agreed upon meaning of the idiom revolves around is something that is primarily concerned with or centered upon someone (or something). In other words, a situation that revolves around characters is a state of affairs or a plight that is centered upon or primarily concerned with the characters. Therefore a paraphrase of the question might be, "What is the state of affairs or plight that primarily concerns or centers upon the characters?"

Thirdly, since no particular characters are singled out, it must be assumed that the question refers to all major characters, who would be the unnamed narrator, Roderick Usher and Madeline Usher. So what situation (state of affairs or plight) revolves around (centers upon or concerns) all three characters? Well, Roderick sought the narrator's company as his guest at the House of Usher because he was suffering some terrible nervous, psychological disturbance. Roderick was suffering this disorder out of concern for Madeline's deteriorating health. He is concerned for Madeline because he feels an impending and horrible doom coming upon the family and manor of Usher. Putting it all together, it is now possible to say that the situation revolving around the characters is the impending doom to the House of Usher, both to the family of Usher and the manor house of Usher.

Enotes has a great study guide for this story.  I have attached the link below.  Here's a general summary to get you started:

Characters:  The narrator, his childhood friend Roderick Usher, and Roderick's twin sister Madeleine.

The Plot:  The narrator travels the Usher mansion after receiving a letter from Roderick.  Roderick complains of having a nervous condition and needing the help of his friend.  It is clear that both the Ushers have some illness.  Madeleine is glimpsed but never approaches othes.  Roderick is nervous and paranoid.  While visiting, Madeleine dies.  Because her condition was "odd", Roderick plans her immediate burial in the family catacombs to prevent having her body examined by doctors.  However, it turns out she wasn't dead.  During a stormy night, she breaks out of her tomb and comes to embrace her brother, who dies with her on the drawing room floor.  The narrator flees the house, which is hit by ligtening, cracking open and crumbling.

Theme:  One of the themes is madness and insanity.  Poe's descriptions point to the the increasing hysteria of the household.  The narrator himself is affected.  Roderick's paranoia and twitchy manner begin to affect his mind and leave us to wonder how much being described is accurate. 

Symbolism:  The crumbling mansion is a symbol for the crumbling state of Roderick's mind.

I think it is important to remember that Poe is described as a "Dark Romantic," which is a kind of school of thought within Romanticism at large but with some notable differences to the main Romantic authors. Dark Romantics such as Poe had a view of the world that emerged from the mystical and the melancholy aspects of Puritan thought. Themes such as the conflict between good and evil, the psychological effects of guilt and sin and the madness in the human psyche were explored. The writings of Poe were all about showing humanity for what it really is - warts and all, removing the masks of social respectability that we often wear and exposing the depths of evil that humanity is capable of.

When we bear this in mind, therefore, this perspective becomes helpful in identifying the "Dark Romantic" elements in this excellent yet terrifying short story. Clearly, the narrator of this piece observes the troubling madness of Roderick and what he sees asks harsh questions about what Roderick has done in terms of interring the body (still living) of his sister. It also asks questions about the hereditary nature of curses, evil and madness and how they can dog families for centuries.