In Norse mythology, Thor’s sister is named Hela, sometimes spelled Hel. She is one of the major figures of the underworld and is associated with death and the afterlife.

Hela is the daughter of Loki, the trickster god, and the giantess Angrboða. Her siblings include the wolf Fenrir and the world serpent Jormungandr, both of whom are feared for their power and destructive potential.
Hela is described as having a half-alive, half-dead appearance, with one side of her body appearing healthy and the other side appearing rotten and decayed. Her domain is the underworld, known as Helheim, which is one of the nine worlds of Norse mythology. In Helheim, Hela presides over the souls of the dead and determines their fates based on their deeds in life.
Despite being Thor’s sister, Hela is generally portrayed as an antagonist in Norse mythology. In one famous story, she is sent by Odin, the king of the gods, to take control of the underworld and restore order to the chaotic realm. However, Hela refuses to release the souls of the dead unless they are offered to her as sacrifices, causing a conflict with the other gods. In the end, Odin banishes Hela to Helheim, where she remains as the ruler of the realm of the dead.
In modern popular culture, Hela has been featured in various forms of media, including comic books, movies, and video games. One of the most famous portrayals of Hela is in the Marvel Cinematic Universe, where she is portrayed by Cate Blanchett in the movie “Thor: Ragnarok”. In this version, Hela is depicted as the firstborn daughter of Odin and a powerful villain who seeks to conquer Asgard and rule the nine realms.
In conclusion, Hela is the sister of Thor in Norse mythology and is associated with death and the underworld. Despite being a major figure in Norse mythology, she is generally portrayed as an antagonist and is feared for her power and destructive potential. In modern popular culture, Hela has been featured in various forms of media, where she is often portrayed as a powerful and formidable villain.