I Just Cast a Spell

"Seriously, I just don't understand. How did you manage to produce that much ice in a place where there's practically no water at all?"

One of the Witches finally asked the question they were all dying to know the answer to.

They had already realized there was no Witch nearby, meaning that even if Magna was a Shadow, he couldn't receive the mana needed to cast a spell without his Witch being close enough.

Besides, even a Shadow as powerful as Arthas couldn't possibly receive enough mana to cast a spell capable of freezing an entire mountain.

They had also considered the possibility that he had used an artifact, but was there even one capable of producing such an effect?

Even their Fire Cannon was a special artifact that required Renna to pour her own mana into it before it could fire.

So, even if Magna had used something similar, he would still have needed an external mana supply powerful enough to produce such an enormous freezing effect.