Demon System, Activated

[WARNING: MATURE CONTENT]
Death by demonic possession--not something well-understood by the general public, but when you are the victim, you learn quickly.

Blake is suddenly thrown into a world of demonic assassins-for-hire when a band of demons killed him by psychic attacks. He finds himself trapped within their hell, and the only escape is to join a Demon System and cultivate enough demonic energies to fight the resident Overlord bosses.

And there are SO MANY Overlord bosses...