Chapter: English Literature During The Romantic Period
Manfred is a Faustian character. Y'know, the jerkhole scholars that summon forth ancient spirits and make pacts with Satan to gain more knowledge. Manfred is, however, an inverted version of this trope: he doesn't seek knowledge, he asks for a way to forget his nebulous past. The ancient spirits tell him they can only grant knowledge, not take it away, so he tells them to screw off.
Then he summons more spirits in different places, all with the same result. This colossal waste of time makes the ancient spirits understandably cranky, so when Manfred asks for death, they spite him and prevent him from dying.
That summary of the story is considerably more exciting than the actual poem and/or play, which has a lot of flowery language and not much else.