The Dark Zodiac

A boy. A blessing. A curse.

A long time ago, the 12 most powerful heroes, The Zodiac, sealed The Demon Kingdom and all its inhabitants away. Knowing that the seal won't last forever and they won't live forever, they use the last of their magic to bless 12 children, each with an Unique Skill, turning those children into Heroes. Whenever a Hero dies, another one with the same Skill will be born. So, like that, when the demons return, they will be sealed off again.

But, who's to say that all Heroes are going to be heroes?