Queen of the underworld, keeper of those who die not in battle
The daughter born to Loki and Angrboða, half of her living flesh, half black as a corpse. Odin cast her into the realm of gloom and set her to rule the underworld of Helheim — those who die not in battle but of sickness and old age all fall under her charge. She is cold, unmoved, and just, and even when the gods begged her to let Baldr return to life, she gave only a merciless condition.
After his death Baldr fell into Hel’s underworld. The gods sent the messenger Hermóðr on the long journey to plead. Hel was unmoved by grief, and coldly named a single condition: if all things in the world, living and dead, would weep for Baldr, she would let him go. The gods nearly managed it — all but one giantess in a cave, who refused to weep.
"Hel" is both the name of the underworld queen and of the underworld itself; after Christianity came, the word evolved further into English "hell," its meaning now far from the Norse original.
Below are how modern works borrow or reinterpret this name or story — not the original material. The two differ, so keep them apart.