So since neither my intelligence nor wisdom are high enough to merge with the practical incarnation I gotta fight him but that guy is a real pain. Whats the best way of killing him? Im a level 14 fighter among my weapons are the justifier, heartgrinder, gauntlets of ogre power and ravels fingernail. What I used to do is punch him with my gauntlets until my health was almost drained then run in circles until im at full health again. This didnt seem to work (does he regenarate?). I know it may be hard to put yourself in my position but strategies would be much appreciated.

Level 14? Aren't you a bit low level for the very end of the game? You must have skipped a ton of content, really.
I've only played through as a wizard, but I ended up around level 20 in the Fortress of Regrets IIRC. I'm sure I could cast level 9 spells even before I got the huge xp reward for merging with previous incarnations anyway.
Also, why do you need to run around to regenerate hp? Don't you have healing items?

Anyway, I've never done that fight since my wisdom was high enough to merge (which is a much better option both story-wise and gameplay-wise), but it shouldn't be that hard if you use items.
He does have a very high strength and constitution, and he does regenerate, just like you (except probably faster unless you have 20+ con).

Do you have any other items you can use in your inventory ? You could eat Cranium Rat Charms until your int is 21 and win the merging process.
Maybe you have some other charms which raise the resistance or armor class versus the damage type the practical incarnation is causing or weaken your opponent.
Do you use the weapon you're most proficient in ?

If nothing else helps reload your save from just before leaving the mortuary and gain more XP and better equipment first.


Practical Incarnation Stats:
HP 128 AC 0 THAC 8 Str 25 Dex 14 Con 19 Int 25 Wis 16 Cha 20

Nevermind, I managed to stab him to death with ravels fingernail. Took me about an hour but I did it. Kthxbai