Caliban both mirrors and contrasts with Prospero's other servant, Ariel.
Prospero had found this Caliban in the woods, a strange twisted thing , far less like a man than an ape.
His punishments of Caliban are petty and vindictive, as he calls upon his spirits to pinch Caliban when he curses.
Homer would have bound Polyphemus with it, and Shakespeare, Caliban.