This character I named Rosaji and the demon that lives in her shadow is called Regthazan.

Rosaji was the daughter of a farmer within a somewhat primitive era. Her family lived within a small tribe of other farmers, she was happy tending to the animals and plants. But a group of savage raiders attacked the tribal village, killing many friends and family in their destructive path. Rosaji tried to escape but was caught by a raider who stabbed her in the left eye when she bit him to try and escape. After being recaptured the raiders dragged Rosaji back to their village located halfway up an active volcano. They dragged her to the top and chained her down to a rock above the magma.

A large looking fellow started chanting in an unknown tongue, causing the magma to bubble and churn as a shadow-like creature emerged from the volcano. With a booming voice it demanded a creature's heart and it scanned those that summoned it. The raiders chose to cut out Rosaji's heart in fear of dying themselves and offered it to the shadow monster. Rosaji died as the creature devoured her heart, then it devoured the souls of the raiders before entering Rosaji's corpse. Her chest sealed back up and life poured back into her body as Rosaji was resurrected. The demon introduced itself as Regthazan and told her that the ritual was completed and she was his new vessel. Regthazan told her that he needed souls of the living and that she would kill people to get them. Rosaji declined at first, not wanting to harm or kill anyone she wasn't a fighter, she was the daughter of a farmer. But Regthazan said its either she does it and chooses who dies or he does it and kills whoever he pleases as she is forced to watch, and he really likes the souls of the innocent. Rosaji not wanting him to kill innocent people sadly agreed but she decided to only go after criminals or overall bad people. Rosaji is no warrior, but she had to learn to fight, even if it meant dying many a time. Regthazan granted her the armor and weapon of his last champion, it was damaged, rusty and old, but for some reason, she felt like his fighting spirit remained within.

Rosaji's body cannot regenerate lost limbs until she has fully died but she does heal at an accelerated rate. Rosaji can keep fighting so long as her will to do so remains, she could be impaled all over and keep fighting. But that does not happen often as the pain can get unbearable when this happens Regthazan drags her into the shadow and sends her away to a safer spot to heal up, and at that time he can restore Rosaji to her previous state when he first met her, which is why her left eye never heals.