What poetic devices are used in "The Listeners" by Walter de la Mare?

Walter de la Mare uses numerous sound devices and literary devices in this intriguing poem. He uses a consistent rhyme scheme in which every other line rhymes. However, while he uses strong rhymes of single-syllable words for most of the poem, he ends the poem on a near rhyme—stone/gone—which is a technique that creates less certainty and corresponds to the unresolved feeling the poem imparts. Some examples of alliteration are "forest's ferny floor," "louder and lifted his head," and "silence surged softly backward." He uses onomatopoeia with the word champed. By omitting the word and from the phrase "their strangeness, their stillness," he makes use of asyndeton.

Probably the most striking literary device the poet uses in the poem is the remarkable sensory imagery. Readers get a strong visual picture with descriptions such as "thronging the faint moonbeams on the dark stair," "'neath the starred and leafy sky," and "plunging hoofs." Other descriptions allow readers to hear the actions of the poem: "knocking on the moonlit door," "air stirred and shaken by the lonely Traveller's call," and "sound of iron on stone." Interestingly, he also describes things that don't happen or that cannot be literally possible: "No head from the leaf-fringed sill leaned over and looked into his grey eyes," and "heard . . . how the silence surged softly backward."

The poem uses devices that stories use, including dialogue, point of view, and suspense. Interestingly, the poem allows the reader to experience the action from the perspective not only of the Traveller, but also of the "phantom listeners." The fact that the reader knows what the Traveller doesn't creates suspense and makes use of dramatic irony. The reader expects that the two parties to this potential meeting will, in fact, connect in some way, but the poem ends without that taking place. Readers are left with a sense of ambiguity: They don't know why the Traveller came or exactly who the "phantom listeners" are.

In "The Listeners," a mysterious poetic narrative, Walter de la Mare incorporates the sound devices poets often use with some techniques that are more common in stories.

The imagery of silence is significant. Walter de la Mare fills the house with images of absence, silence, and even death. The listeners are "phantoms." Taken literally, this could mean they are dead or absent, but it could also imply they are there in the house and just refuse to answer the Traveller. Even though the Traveller might think people are actually home, those people might as well be phantoms because they refuse to answer him. The listeners are in the "quiet of the moonlight" and the Traveller is the "voice from the world of men." This imagery suggests the listeners are part of nature itself and the traveler is a lone man asking questions but receiving no replies. The latter is more philosophical because it suggests a man asking questions by himself.

Taken literally, this is a man asking for communication at the door of a house. One could interpret the poem in a broader metaphorical way, though, by arguing the poem shows how every individual seeks communication and acknowledgment from others. It is a social yearning we all have. It also describes the experience of how every individual asks questions (of other people, God, or nature) but does not always receive a response. So, metaphorically speaking, the Traveler is anyone who seeks these things. In this way, the entire poem is a literary device: a metaphor of how every individual reaches out for answers.

As the Traveler leaves, the listeners wait for the noise to fade away. The poet uses alliteration to suggest the sound of a light breeze, whispering, or a susurration:

And how the silence surged softly backward

What similes and metaphors are used in the poem "The Listeners" by Walter De La Mare?

Walter De la Mare's "The Listeners" uses the metaphor as its central conceit, as indicated in the title, though the poem does not present many discrete examples of metaphor or simile. 

The most significant metaphor in the poem is the one that suggests that "phantom listeners" exist in the house where the narrator comes to knock and receives no response. Silence or emptiness thus becomes identified with phantoms in an extended metaphor. 

But only a host of phantom listeners   
   That dwelt in the lone house then
Stood listening in the quiet of the moonlight   
   To that voice from the world of men

"The Listeners," by Walter De La Mare is remarkably lacking in its use of metaphor and simile.  The poet describes almost everything in this poem with straightforward, literal description.

The door of the house is "moonlit"; the window-sill is "leaf-fringed"; there is a "dark stair" and an "empty hall"; when the horse walks away from the house, we merely hear "the sound of iron [horseshoes] on stone." 

One of the only metaphors in the poem is near the end, where the poet describes how "the silence surged softly backward."  Silence, of course, cannot surge; rather, the poet is comparing silence to an ocean wave that surges "softly backward" as it heads back out to sea after crashing on the beach.

How does Walter de la Mare engage the reader with elements of mystery and the supernatural in his poem "The Listeners"?

In this question, you're being asked to examine how De la Mare develops the reader's interest through his use of various literary techniques as well as the supernatural and the unknown to create intrigue.

The first point to explore is the way De La Mare introduces the setting and situation. We begin in media res, in the middle of things—the unnamed, unknown traveler is "knocking on the moonlit door" at the beginning of the poem. We do not know who the traveler is or who he is hoping to find at the abandoned house. He is "perplexed and still," as are we, the reader. Note also the gothic element of the bird which "flew up out of the turret," creating an atmospheric sense of the house as home only to animals.

Next, however, the poet introduces the "host of phantom listeners." The terminology here is eerie: they are described using such an active term; they are defined by the fact that they listen to others, and yet do not respond. Their listening is so intense that the traveler actually experiences it as a "strangeness," a response to his question. The horse, too, "moved," as if even he were aware of something existing in the house.

The listeners say nothing, as their name would suggest, but the traveler still responds to them, telling him that he "kept [his] word." Again, this one-sided conversation evokes intrigue in the reader: we do not know what the traveler has promised, or to whom he has promised it. The poet leaves the whole situation open for the reader to interpret as he or she sees fit. We are left to imagine who was in the dark house before the "listeners," and what once happened there. The house itself is now described using a host of eerie and evocative terms—"shadowiness," "still," "dark," "lone"—and the traveler is the only person "left awake" in it.

Note the ending of the poem, however—the point of view here is not that of the traveler, but of the listeners. We, the reader, are left with them as they listen to the "plunging hoofs" "surging" away as the traveler leaves the woods behind once more. The suggestion here is that the listeners will remain.