Ursula mentions at the start of The Little Mermaid that she was once esteemed and lived in the royal palace. In early adaptations of the film, Ursula was King Triton's sister, and therefore, Ariel's aunt, which would explain her living in Atlantica. In the Little Mermaid TV series, it is implied that Ursula was exiled after attempting to create duplicate copies of the trident to start an army with. She sought power over Atlantica