Nightkeeper

It came to her when she was a child. It whispered truths in her ear of the wolves of the Nightstriders. Of Vesna and Stargaze, and all those that had been allowed in this pack. It promised her so many things, told her of its importance, of its power. She had always been so susceptible to darker thoughts. And this lone, dark soul latched onto those thoughts like an open invitation and infected her. And she welcomed it in.

The pup began to change. Eyes turning darker, slowly but surely. Shadow growing deeper. The very air around her began to vibrate with the darkness that was slowly spreading through her body. Wolves that spent too much time around her in the dark found themselves growing weaker. After a few nights of waking up sick and exhausted, one of her littermates never woke up and no more light shone from her eyes.

The wolves began to fear her. Some...were intrigued. She was allowed to stay, of course - the Nightstrider's have always been a place for the lost, and Vesna foolishly placed too much trust in her own blood - but there are some that know her coming marks a change for darker times.

And they were correct.

She drained the life from Vesna first and took control. Stargaze went next, and Mercury soon after. The last remnants of the old leadership lay before her, blood no longer flowing from their wounds, skin dried and cracked as all that was living within them was ripped away. It was a day of blood and tears and it was, for her, a sacrifice. A baptism. She bathed in their misery and wings of night burst from her shoulders and no light would touch her eyes again.

From then on, she led the Nightstriders truly into the dark. A pack and a cult, following out of love, fear, and awe, behind the footsteps of their unholy priestess.