Corruption of Spirit

[sffp]

So I finally have a kobold nec at a high enough speed/stealth/con combo that it may be a viable contender when I came upon The Corruption of Spirit book in the Black Market (150,000 smackers). That would have about bankrupted me but I hadn't seen it before so I started looking at the spells - and they all suck?

50 HP - 50 SP swap - I admit that sometimes I need extra damage to send larger HP foes when I'm low on mana, but 50 SP doesn't seem near enough for 50HP. It will cost me an action, and only let me throw 4-5 more disenchant or 2-3 more annihilate. resorting to <shudder> archer or wands feels like a better deal

Crush- feels like a flea killer and isn't really needed - usually low HP creatures aren't the problem

Vampire form - Another shapeshift where I won't be able to cast? I like to warg, but I take too much damage not to change back often

The other two I couldn't learn yet, but Curse costs 100HP and might be useful against big hitters but maybe not - seems risky to cast

Same with command - how does that actually work

I left the book in the store and bought a strength potion instead...