What is the significance of this quote to the play as a whole? "Thou shalt be lord of it, and Ill serve thee."

Caliban is trying to convince Stephano to kill Prospero. Caliban says that if Stephano can rid him of Prospero, he will let him (Stephano) rule the island and he (Caliban) will serve him. Here Caliban is trying to upset the natural order of this magical island as it was once upset on the mainland.