Zerxus was still in control, at first. You don't take the oath he did, with the power he has, and lose your temper on a regular basis. But the rage kept building, and maybe if it was aimless fury alone he could bear it, but it wasn't. He could hear Asmodeus whispering to him from the start, urging him to give in, alternatively flattering his strength and laughing at his weakness. He could hear Xartaza, as if he held the mace in his hands (and sometimes, that's how his sword looks as he swings it down).

It helps that he hears Evandrin too, sometimes; Evandrin, and Elias, and the Ring of Brass. He even glimpses them out of the corner of his eye, reminding him of who he was, who he can still be on the Barge. And when that fails, there are others who've been able to stop him from going too far.

Still, at this point his armour is drenched in blood, and his movements are stiff with pain and weariness. When he sees Jedao, his eyes narrow; he knows at this point that he can't entirely trust what he sees, but he draws his sword just in case. It alights in flame that casts no heat, though the steel itself is stained with viscera.

"Jedao?" Violence is a weapon of last resort. It's been a common reverb since this started, chanting his oath to himself.

He's still present enough, sharp enough, to grasp the Jedao is containing his own fury. He lowers his sword, but doesn't sheathe it.
"If I try to heal you, will it work?"

Pathetic, Asmodeus hisses in his ear. Look at him! How many times must your trust be broken before you learn?

Reflexively, his grip on the hilt tightens, but he couldn't say who exactly he wants to swing the blade towards.