ToME: the Tales of Maj'Eyal

I'm in the dimensional rift which I've done a dozen times before without issues. Playing a level 18 brawler and literally everything I do heals him. I killed the Clone without a problem. I have literally taken everything off and I still heal him for 10HP every attack, with gear it's more like 40% HP lol.

I cannot leave. I cannot kill him. Am I seriously softlocked in a roguelike?

And why the hell does he have absorption? And of WHAT? The message log just says he's hit for 'healing'.

He most likely rolled Penitence (a staff) as weapon and it grants 20% affinity/30% resist to the chosen element, which would be Physical.