your uncle is a traitor and killed your family in a cunning way for the sake of a royal throne and thought you too were dead.

then your uncle became a king, sure you didn't accept that, hatred and revenge took root in your heart. you summoned a demon to take revenge.

the ritual was successful and a demon appeared "i beg you to help me for revenge, i'll go to hell with you for that!!" he smirks in satisfaction when he sees the hatred in your eyes.

"your application is accepted~"