What role does Circe play in "The Odyssey."

Circe is a witch or enchantress in the Odyssey.  She
turned Odysseus' men to swine when they drank the sweet nectar she gave them.  Odysseus
was the only one who drank the nectar and was able to remain human because Hermes gave
him moli to eat to protect him from Circe's spell.  Upon surviving Circe's spell without
being transformed, Circe then told Odysseus she would only turn his men back into their
human form if he would take her to bed.  He did.  He stays on Circe's island a year
before traveling to the Underworld.