One of the things that students often struggle with in reading the morality plays is the allegorical characters. Allegorical characters and personifications are actually one of the things that define the morality play.
David Bevington, in his book Medieval Drama, defines the morality play as “the dramatization of a spiritual crisis in the life of a representative mankind figure in which his spiritual struggle is portrayed as a conflict between personified abstractions representing good and evil”, and, though it does not catch all of the surviving examples, this definition is a good starting point.
Allegory can be a difficult literary device to understand and explain: it is a form of metaphor in which abstract ideas or principles are represented as concrete characters, figures, or events.
What does this mean? Well, rather than the writer spending any time or energy trying to make a character resemble a “real person”, or to be emotionally convincing, complicated (in terms of personality, behavior or action) or surprising, the writer makes a character simply represent – or personify – one attribute. Rather than a character being “Hamlet” and full of contradictions (maybe a coward, maybe a brave avenger; maybe a misogynist, maybe a good boyfriend and son; maybe a Protestant, maybe a Catholic) you have a character called “Fellowship”, who simply represents the idea of fellowship.
It is a far simpler, less rich, less complicated view of character than the modern one. It also means that there is a strange double vision in the way that the play works. When Fellowship speaks, you are hearing the words of the character Fellowship, friend to Everyman – but you are also hearing an attitude that might be in some way associated with fellowship. If strength could speak, for example, what would it say?
Critics have, in recent years, really emphasized the problems of combining the moralistic and the dramatic in this way; and it has become one of the richest strains in examining the morality plays critically.
There is one thing to watch out for, though: the moralities are certainly often peopled by – as Bevington suggests – “personified abstractions” and allegorical figures (Strength and Mercy are two examples from Mankind and Everyman respectively), but there are also more general types (such as Fellowship and Cousin from Everyman). It's also important not to forget those exceptional characters who appear as themselves (God and Death in Everyman and the popular devil character Titivillus in Mankind.