Allegory is the primary literary device used in the morality play Everyman, but symbolism and personification are also present as well as irony.
Let's look at allegory first. In an allegory, characters represent abstract ideas or groups of people. Everyman, the title character, literally represents every man or all human beings. This play presents the spiritual journey of life and death and judgment that every human being faces. The other characters are also allegorical. Goods, Riches, Beauty, Knowledge, Fellowship, and the rest represent the qualities their names indicate.
Symbolism and personification intertwine with allegory. Death, for instance, while being allegorical, is also symbolic, for he represents the unavoidable end of every person's life. Everyman's character at some points symbolizes sinful, fallen humanity while later representing repentant, saved humanity. Personification also appears as Confession is personified as a character. The other characters, too, may be considered personifications as well as allegories and symbols. These devices work together in deep and fascinating ways.
Finally, there is irony here. The friends Everyman relies on to go with him to judgment all leave him. He cannot depend completely on any of them even though they do help him. Only Good-Deeds goes with Everyman to meet God at the judgment.