Wear feather cape, find the stairs, run and throw fireballs. I liked the boss because it was quite different from all the others.

Recovering lost items is the only conundrum, but so long as you keep at a distance, it's possible to handle it. If you're starting to run out of resources like forsaken powers, rested bonus or potions, you can always jump down (with feather cape) and try to make it for the exit?