For 10 points, name this only female avatar of Vishnu.
In a story from the Ganesha Purana, this figure steals Virochana's magical crown. This figure grants Aravan a boon by marrying him and spending a night with him before he sacrifices himself to ensure the victory of the Pandavas. This figure tells a demon that she will marry him if he can imitate her dancing, making him touch himself on the head, which proves his undoing since he has the power to turn anybody to ashes by touching their head. That demon is named (*) Bhasmasura. The god Shasta is born after Shiva ejaculates on the ground while trying to seduce this figure. A god takes this form in order to seduce the asuras into giving her amrita after the churning of the ocean, so she can give it to the devas. For 10 points, name this only female avatar of Vishnu.
In a story from the Ganesha Purana, this figure steals Virochana's magical crown.
Mohini [prompt on Vishnu; prompt on Krishna, because in the Aravan story she's an avatar of Krishna]