"Beautiful she may be, don't trust her. She loves you as long as you're useful, not longer than that." -Rosaria Fair-Garden to Allochval Songblade.
Xin Yue is the Spirit of the Dark, created by Qipian to be his servant. She takes the form of a beautiful woman with dark skin and hair, and her sacred grounds are shadows and darkness, anywhere there is darkness. She can exist anywhere, but will only choose the darkest places to manifest. She is also the creator of The Shadow Hood. She is also notable for having corrupted a party of adventurers millennia ago, leading to the creation of The Dark Races.
In the quest to end the never ending Winter, The Children of Frost braved many dangers. Taking advantage of this, following the death of Fenrir Wolfsbane, the first member of the party, Xin Yue approached him, offering him freedom from death's grasp. Accepting her proposal, Fenrir was brought back from the dead, at the cost of becoming cursed. Xin Yue benefits with the death and revival of fallen party members, using the side effects of the curses inflicted to enact her plans throughout the world.