She also develops a romantic relationship with another mortal to wield Thor's power, Eric Masterson. Despite this, Sif risks her life to travel to the realm of Mephisto to free what seems to be the soul of Thor from a mystical bag, pledging her loyalty to the demonic entity. She is manipulated into a new costume change and is sent to face down Eric and Balder in battle, who had willingly followed her, worried for the success of her mission. Eric and Sif eventually part realms as friends, but he leaves her with a favored leather jacket.