pron. kahTAHbuhsis
A Greek word and literary term from the prefix kata- (down, below) and the verb -bainein (to go). A going down below, which refers to a hero's journey to the Underworld. Something that all great heroes do!

Odysseus journeys to the Underworld to see Teiresias the blind seer in Book XI of Homer's Odyssey, in order to find his way home. The witch Circe gave Odysseus the task and instructions, which included sailing to a rock at the junction of the rivers Pyriphlegethon and Cocytus into Acheron, digging a pit for the pouring of libations, and animal sacrifice. Upon Odysseus' descent, he has the opportunity to see a number of shades from his lifetime. A few of them: Achilles, Agamemnon, Ajax, Ariadne, Jocasta, Sisyphus, Tantalus, and Teiresias.

Aeneas' trip in Book VI of the Aeneid by Vergil. "Easy is the descent to Hades: night and day the door stands open; but to recall the steps and pass out to the upper air, this is the task, this the toil!" (The Cumaean Sibyl to Aeneas. Aeneid 6.126) Some of the souls Aeneas sees: Anchises, Dido, Palinurus, Pasiphae, and Phaedra.

According to Greek mythology, as one of Heracles' Twelve Labors, he descends to the Underworld with the task of capturing and bringing back Hades' three-headed dog Cerberus, who guards the entrance to the Underworld. Hercules undergoes the mysteries at Eleusis with the hopes that they will aid him. After some minor incidents Heracles asks Hades for Cerberus and the god replies that he can take it if he can master the beast without weapons. So finding the three-headed hound at the gates of the river Acheron he grasps it without relaxing his grip, and although the dragon in Cerberus tail bites him, he at last gains control. Yet it is also told that Heracles received Cerberus in chains as a favor of Persephone, who welcomed him like a brother.