The undead couple that appeared at the graduation party were underlings of "Lich Oberus," one of the Four Heavenly Kings of Luminor Academy.

In the original story, these monsters were never meant to appear at the academy. Particularly, with Kelton's massive build, it’s impossible for him to cross the small bridge leading to the Isle of Knowledge. Let alone without anyone noticing.

This means that there’s likely a Lich capable of summoning Kelton’s enormous body lurking somewhere in the academy.

Facing both a Heavenly King and their direct subordinates simultaneously created an unbelievably harsh battle environment. There wasn’t even time …