Kai will
Spoiler!
Put a mark on his brother Ares, that will cover his hero mark. The people will believe the hero Ares, also have an evil mark like Kai. Kai will declare himself a demon king, while demon king Griselda will become his subordinate. Kai's revenge on his family, has him slice his father's arm and burn the marquis mansion, to show himself denouncing his family(who will betray him anyways). Kai willenslave Erza. Saint Johann will be turned an undead by Kai.
