Think of this, if not that, then:Fight-Or-Flight.
Its obvious K2's Assassin planned on the black-text-thingy to be a killing blow. This, we know, is true. Ace, while magically inept(I think...Wasn't that his reason to use Essence?), realizes the power is off the scale for a friendly spar. He sees no chance at protecting himself from death by fending off his attacker, being surrounded, so he cuts his losses and runs like the devil was on his tail through a alternate means of escape, randomly headed for Terrorguove.
Fair enough?
Meh, didn't know it was normal, for his characters to flee, Nisorin. Still, this hardly seems worth dyin' for...