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 to question why such a situation had arisen.

‘Just dealing with those bastards alone is already a colossal pain in the ass….’

Venari and Kelton were incredibly difficult boss monsters to handle, even in the original story. Despite not being one of the Four Heavenly Kings, their difficulty was on par with fighting one.

With their immunity to physical and magical attacks, tricky healing patterns if not attacked under specific conditions, and even a second-phase "low-health" pattern, they were essentially nightmares.