This spell... it's at the end of the tree and summons a single monster found on level 2. No more than that single monster either. The problem is that it's just horribly weak, especially for where it is. I'd personally suggest one of two things: Resurrect the monster itself and take control of it. This would need to have some limiting factor but at least it's implemented and possible. Make the number of summonable zombies infinite/incredibly high. At least in this way you could get an army of little meatshields.
I was just working on rebalancing the core skills and I've never tried Zombyfication. So it really is as vulgarly underpowered as it seems, huh? Good to know. Can you point me in the direction of the ressurect-and-charm code, because I'd love to work that into my rebalance.
Well, resurrection is the name of the effect type that resurrects (must target a corpse), and charm is the name of the effect that charms. Keep in mind you must charm it AFTER you resurrect and thus it needs a separate spell to be triggered.
NP. This skill is just terrible. I mean it's the second-to-last skill in fleshsmithing, and consumes a corpse to summon a monster found on level 2. It can't carry you through anything like mustache golem (which I remind you is a level 2 skill). It's exactly the strength of any enemy on floor two.