"With Arbatel's power and my genius I have created a being in my image, and she is perfect." - Belial
Arbatel wanted a daughter, so he went to Belial -- a mad genius in his own right -- for help. Together they crafted a new angel. Arbatel wished for her to be more like Belial, and less like his species yet still retain the great power associated with Soul Collectors.
This is Sammael. She is a character that appears at the end of my novel and is intended to play a significant role in the second.