Kang Oh wasn't a Grandmaster. However, he was much stronger than your average Master.

He was on the cusp of becoming a Grandmaster. Then you factor in Gluttony, which multiplied his abilities several fold, as well as Demon Sword Ubist, which was the mortal enemy of mages and souls.

These factors combined allowed Kang Oh to fight Katan on even footing.

Kang Oh focused entirely on overwhelming Katan. Ubist dealt so much damage to souls that Katan's HP instantly went below half.

However...

Katan was called the Worst Mage for a reason. There was no way things would end this easily.

"Hehe, let's have some more fun!" Two large, sharp horns sprouted from his forehead.

Demon's Horns!

This was a Black Mage secret move. It had a similar effect to a normal mage's Overload. It amplified the caster's magic power significantly.

Moreover, it gave the user almost infinite MP.

However, this ability couldn't be used for very long; it ran the risk of transforming the user into a demon that lost all traces of their former intellect.

Roar!

Two giant dark red fireballs ignited in his palms.

Annihilating Fireball!

Roar!

The fireballs came flying at Kang Oh one after another.

Kang Oh stomped on the floor, summoning an ice wall. Unfortunately, the flames were too hot, so the wall...