Mythology Creatures

Demon Contract

There are lots of different ways you can take a demon contract book but here is my favorite.

Main is kidnapped and used as a sacrifice or host in a cults ritual.
Main creates a pentagram on purpose.
Mains at the wrong place and time.
That maybe Main lives in a cult and it's his turn to do the ritual.
Or a demon slayer school where inorder to have powers Main must make a contract.
Whatever you fancy.

The demon is bond to Main vea being brought into the world using Main's blood. Wherever the blood came from there would be a "tattoo mark" there.
With the contract mark the demon is always connected to Main even into death.

But the pluss are Main can see demons this might greatly help if Main might become a demon slayer. Main's demon can also turn into a weapon.
Then the negatives are demons have an extreme sex drive (they know how to pleasure their human contract), ravnish hunger, a strong temper and uncaring nature.

The appearance of a demon greatly varies from demon to demon. In the human world its not uncommon for them to shape-shift into a random human body. This as you can imagine can be quite a dangerous ability and the demons know this often ruining one's life or driving them insane as the quicker their contract human dies the quicker they can go back to Hell.

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Interesting sides to this are Main being too wild for the demon. The demon gets attached to Main so he uses that as an advantage or the demon gets attached to living in the human world so he doesn't want Main to die.