Lilith

Born in the early days of civilization, and cursed for disobeying, Lilith was forced to a life of suffering; Immortal, forced into a beastly form, only free of her beast skin on the night of the full moon. She claims a swath of forest as her own territory which she guards ruthlessly, killing anyone who steps foot in it. She eventually met Isaac, who had wandered through her forest. After he survived her attack, the two spoke and began to bond over their similar curses. Lilith puzzled out what made his tick, figuring out he was a litch, and the souls he absorbed were stored somewhere and what fed into his life. His curse, she reasoned, would be the key to ending her life- if he absorbed her infinite life force, it would let her finally die- at the cost of his souls never running out, thus dooming him to her true eternal life. She grew to care for Isaac, her only real friend, and thus didn't want to burden him. However, after a brutal attack on her forest, Isaac found her wounded, and she begged for him to kill her, expressing how cruel and painful it is to stay alive longer than you should. Isaac would do as she asked, the event leaving a dark scar in his heart that would lead to him shedding his name and humanity and working to bring about the natural end of all things.