CALIBAN: No, pray thee.
[Aside.] I must obey. His art is of such power
It would control my dam’s god, Setebos,
And make a vassal of him.

– William Shakespeare

The Tempest, Act 1, Scene 2. Caliban begs Prospero not to carry out his threat to inflict more pain on him. Speaking to himself, he concedes that he has no choice but to obey Prospero. His magic powers are so great that could even defeat Setebos, the god his mother used to worship, and make him a servant.