Nephthys was the sister and wife of Sutekh. While her husband was trapped in a pyramid on Earth by the Eye of Horus, her mind was split up into two parts: her instinct, stored in Sadan Rassul's daughter who was mummified alive, and her reasoning in a canopic jar. The reason for this punishment was that she was judged more dangerous than even Sutekh.
Her reasoning was released in 2000 BCE when robbers were plundering her pyramid and broke the canopic jar in which it was stored. (PROSE:The Sands of Time)
Behind the scenes
In Egyptian mythology, Nephthys was one of the Egyptian goddesses, a guardian over the dead, alongside Isis, who guards the canopic jar containing the lungs.