The prophecy
Once every thousand years, a red moon appears called the blood moon. When this blood moon rises, an evil spirit escapes from hell to murder and assassinate the innocent, sucking the blood out of them as they do. They cannot age and normally have a high IQ. When the spirit has killed enough people, they can choose to keep a few bodies and give them life, making them doomed to follow orders from their master. But, the spirits always have one thing in common: They must give a challenge. When the spirit announces their challenge, people may choose to accept that challenge. If they complete the challenge the spirit must kill him/herself and so do their minions. If they are unable to complete the challenge the spirit gets to kill the person. This is the story of a spirit who spawned into the world and did something unexpected, but fatal to all who challenged him.