Bleaty is an unbalanced boss. It can only be defeated using CYDSTEPP (unless you use the gnome + Jehora Jeheyu combo, but I'll assume you haven't unlocked Jehora yet).
Here's some advice:
Try a physical approach. Use a halfling with the tri-sword and try to find the CYDSTEPP glyph (or HALPMEH, if you're a wizard).
Do not convert your glyphs right away, only when you need health potions (unless you are worshipping Taurog).
Save exploration space. If you kill a high level enemy, you get an experience bonus, so you won't need to waste your exploration on same-level enemies...
Bosses will One Shot me most of the time
The only bosses I remember having trouble with at the beginning are Aequitas and Bleaty, and they can be defeated using CYDSTEPP because of their low HP.