Lich reborn as a magic school student

Eight centuries ago the kingdom of Vutia flourished as one of the strongest nations of the continent. Protected by the great Archmage of Vutia, Kashra. However, the gods favored the rising Habarene empire and Vutia fell. However, from the ruins of vutia arose the Archmage on a quest for the restoration of his kingdom. Kashra ventured into many lands fighting alongside many legendary heroes. However, in these adventures, Kashra fell to dark magics, and his goals and ideals were slowly corrupted. Restoration of his kingdom at the end meant total sovereignty over the continent. However, the gods were not happy with Kashra and thus sent forth a hero to kill him. This hero succeeded and the age of darkness ended. However, in another dimension, a young student who had lost all purpose in life chanted once again the long-dead mantra of the dark armies of the lich king Kashra. In a bid to summon a demon from that dreadful army, he instead summoned the lich king himself. And thus, Kashra was reborn as a student in a modern magical school.