Soul Trap

This is the story of a girl named Scarlett. She's attractive and a bit of a total bitch. When she comes across a strange stone, she plans to make some money. Instead she's sucked into the stone and talked to by the Grim Reaper himself, who shares the truth about her upcoming death, and offers a way for her to live that she doesn't like. She wakes up believing it was all a dream, and tried to go back to her normal life. However she is soon ravaged by vicious and brutal hallucinations. She realizes she may need to kill to stay alive.

That stone was the key to her insanity.