Narrator of "Sir Eustace Grey"
The narrator of this poem appears to be insane, but in his mind, he is a protagonist. However, he is now located in an insane asylum after he killed the lover of his wife. After finding out that his wife was cheating on him, he immediately tracked down the man she was doing it with and killed him, and this murder led to a large array of mental issues for him.
George Crabbe
The actual author of the poems, Crabbe is seen through much of his poetry. Whether being that narrator of the poem himself or simply another narrator in disguise, it is often easy to distinguish the themes of Crabbe's poems, because he wants them to be evident. One of these themes, for example, is the negative effects that alcohol has on your life. Although not being the direct narrator, Crabbe gets his point across through the words of another.
Rupert
The main character of the poem "Procrastination", Rupert discovers the effects of waiting too long to do something. After waiting to see his lover for a long time, he discovers that she is now greedy and selfish, likely because he was absent for so long. He now realizes that this is simply human nature, and he should have jumped on the chance to be with someone that would truly love him.