The mood of 'The Conversation of Eiros and Charmion" is an odd one to identify. It is an other worldly mood of safety following a mysterious suffering. Mood is the atmosphere of overall emotional feeling of a story;it may be consistent throughout or it may change from section to section. Mood is different from tone, which is the narrator's attitude toward characters and events. Incidentally, in "The Conversation," there is no narrator, so tone is supplanted by the tone of Charmion's voice, since he acts as the moderator of the conversation and the scene. Mood is determined by the setting, the diction, and the characterization in the story.
Diction, which contributes to mood, is the writer's choice of vocabulary for expressing an idea. An example of diction can be seen in Eiros's discussion of the "individual calamity." He is discussing comets and might have said, "Scientists said that comets were made of ice and not long lived and so no threat to our planet." Instead, Poe chose a more elevated and learned diction so that Eiros actually says: "We had long regarded the wanderers as vapory creations of inconceivable tenuity, and as altogether incapable of doing injury to our substantial globe, ...."
The mood of "The Conversation," then, is determined by the unidentified other worldly setting in "Aidenn," where knowledge overwhelms ("I am overburthened with ... the unknown now known.") and "the film of shadow" is removed" from eyes. The mood is also determined by the characters who are not described but only revealed through what they say. For example, Charmion’s characterization of kindness is revealed when he says, "You have now suffered all of pain, however, which you will suffer in Aidenn." The mood is further determined by the learned and deliberate diction with which both characters speak. There is also a note of wild desperation in Eiros's diction when he chooses how to describe the "calamity": "I shudder while I speak. ... For a moment there was a wild lurid light alone, visiting and penetrating all things." Therefore the mood can be said to be one of calm in the midst of remembered despair.