This is a monologue, an imitation in the form of action, with only one narrator.  As the Duke gives the Count’s ambassador a tour of his house he utters many “speech acts” as he utters what is ostensibly the speech-act “to inform.”  He describes the portrait, the statue, etc., but in doing so, he reveals his overweening pride, his avarice, his emotional coldness, his violent and possessive attitude, and other character flaws. The main literary device is "irony." Irony means “What goes out as A comes back as non-A.”  That is, the author reveals true character by making the narrator, as he tries to convince the ambassador that he would be a good match for the Count’s daughter, say things that the ambassador will bring back to the Count (the ambassador is there not merely to suggest the liaison but to report back on the worthiness of the Duke for the match.)  But the ambassador's report will be the opposite -- that the Duke is avaricious, cruel, insensitive,and a braggart, and ignoble in many ways. If by literary devices you are referring to poetic linguistic devices such as metaphor, no; this poem works as realistic speech, a monologue.  The key is to look closely at the speeches – what, besides information, is revealed by the Duke’s final utterance about the bronze statue?  Browning uses this form in several of his poems.  (Cf. “Fra Lippo Lippi” )