Sophia Hapgood possessed an Atlantean necklace where Nur-Ab-Sal had transferred his spirit. The necklace was perhaps one of the artifacts found in the Jastro expedition, which Sophia kept for herself.
Sophia never separated the necklace and she claimed it guided her. When she was reunited with Indiana Jones, he suspected it had some kind of negative effect on her.
When they reached Atlantis, Nur-Ab-Sal's spirit took over her, but Indy got rid of the necklace, freeing Sophia from its control.
Behind the scenes
The necklace differs significantly between the comic book appearance and the video game appearance. In the comic it is an indifferent necklace composed of beads.
In the game, the necklace is a geometrical horned face with an open mouth that can receive Orichalcum, although its usage is never explained. Also in the game its role is more sinister since it is revealed that Nur-Ab-Sal wanted to take control of Atlantis again, by guiding Sophia through it.
In the comic, the necklace ended with Hans Ubermann during his attempt to use the God machine, while in the game, Indy threw it in a lava pit, destroying Nur-Ab-Sal's spirit.