Final answer:
Chryseis plays a significant role in the Iliad as the captured daughter of a priest of Apollo, whose return is demanded to end a plague sent by Apollo. Her capture sets off a chain of events in the poem.
Step-by-step explanation:
Chryseis plays a significant role in the Iliad as she is captured by Agamemnon, the commander of the Greek army, and becomes the center of a conflict between him and Achilles. Chryseis is the daughter of a priest of Apollo, and when her father tries to ransom her back, Agamemnon refuses. This act angers Apollo, who sends a plague upon the Greeks. To appease Apollo and end the plague, Agamemnon is forced to return Chryseis to her father. This event sets off a chain of events and serves as a catalyst for the conflicts and battles in the epic poem.