Thanks, that's mostly helpful. The Wicked Mask however is the most common encounter on B1 of the Lunar Core, so finding him isn't a problem.

I've noticed after loading a save\quicksaving that the first enemy fought in the core is a Behemoth, after running away, the next 20ish fights are consistently Wicked Masks. After about 30+ fights, the most common encounter is Red Dragons and occasional Behemoths. Quicksaving resets the encounters of course.

dealing damage (exact amount)
Would you suggest using attacks that only deal 9999 dmg then? Would using the defend command affect anything?

Hope this info helps anyone else searching for the Glass Mask.