Katabasis
One of the most famous examples is that of Odysseus, who performs something on the border of a nekyia and a katabasis in book 11 of the Odyssey; he visits the border of the realms before calling the dead to him using a blood rite, with it being disputed whether he was at the highest realm of the underworld or the lowest edge of the living world where he performed this.
The trip to the underworld is a mytheme of comparative mythology found in a diverse number of religions from around the world.
The nature of the quest differs; sometimes an object or the rescue of a loved one is sought, while in other stories knowledge and secret revelations is the goal.
The ability to enter the realm of the dead while still alive, and to return, is proof of the classical hero's exceptional status as more than mortal.
A deity who returns from the underworld demonstrates eschatological themes such as the cyclical nature of time and existence, or the defeat of death and the possibility of immortality.
[1] A katabasis is in general followed by an anabasis (a going up) to distinguish itself from death; very rarely does a living hero decide to stay in the Underworld forever.
Famous examples of katabases in Greek mythology include Orpheus, who enters the underworld in order to bring Eurydice back to the world of the living, and Odysseus, who seeks to consult with the prophet Tiresias for knowledge.
[3] Odysseus sets out an offering of honey, milk, wine, water, and barley before slaughtering two sheep to add fresh blood to the meal.
[12] Odysseus then sees a list of women whom he only briefly mentions: Phaedra, Procris, Ariadne, Maera, Clymene, and Eriphyle, all also lovers of gods or heroes.
[15] Odysseus then begins seeing figures of dead souls who do not talk directly to him: Ajax, Minos, Orion, Tityos, Tantalus, and Sisyphus.
[18] The priestess tells him to find the Golden Bough, and if the branch breaks off in his hands, he is fated to go to the Underworld.
[20] Aeneas first encounters several beings and monsters as he enters: Sorrows, Heartaches, Diseases, Senility, Terror, Hunger, Evil, Crime, Poverty, Death, Hard Labor, Sleep, Evil Pleasures of Mind, War, Family Vengeance, Mad Civil Strife, Scylla, Briareus, the Hydra, the Chimaera, the Gorgons, the Harpies, and Cerberus.
[25] Next, Aeneas sees heroes of battle: Tydeus, Parthenopaeus, Adrastus, Glaucus, Medon, Thersilochus, Polyboetes, Idaeus, Agamemnon, and Deiphobus.
In book 4, he includes an account of Juno's descent to Hades to bring her perceived justice to Ino.
[30] Juno seeks the Furies (Tisiphone, Megara, and Alecto) to destroy the house of Cadmus, namely Ino and her husband Athamas.
[32] The next major katabasis in the Metamorphoses occurs in book 5 by Proserpina, the daughter of Ceres, who is kidnapped by Dis.
As Proserpina is picking flowers, Pluto falls in love with her and decides to grab her and take her to the underworld in his chariot.
Overcome by the heartfelt song of Orpheus, Proserpina calls Eurydice to leave with her husband–on the condition that he does not look back until he reaches the exit.
