Cult of Diablos

The MC made up a story about the 3 heroes, after slaying Diabolos, were cursed by the Demon and all their descendants became victims suffering Mana Deviation. The porters of this decease were respected by the people because it meant that they were the heroes descendants. Later on the Order of Diabolos manipulated the truth and they became hated by the folks and rejected with the name of cursed child etc...

In fact, everything the Mc is true but he don't know that.

All of the heroes who fought Diabolos were female. That’s why the Curse of Diabolos only manifests in females.