In Greek mythology, Hades ruled the Underworld as Persephone’s husband.
Hades was one of the three sons of Cronus and Rhea who divided the cosmos after overthrowing the Titans. Zeus received the sky, Poseidon the sea, and Hades the realm of the dead. Hades was therefore not the god of death itself; Thanatos personified death, while Hades governed the dead and the Underworld.
The myth of Hades and Persephone explains the seasonal cycle in many later interpretations. Hades took Persephone to the Underworld, and her mother Demeter’s grief caused the earth to become barren. Persephone eventually spent part of each year below and part with Demeter.
A common mix-up is treating Hades as equivalent to the Christian concept of hell. In Greek myth, his realm included several regions, including the Asphodel Meadows, Elysium, and Tartarus, rather than being a single place of punishment.