I bought some Inflict Serious Wounds pots at the Portable Hole. The spell description says "Target: Foe or Undead Friend".
So I wanted to test it, found an undead friend, put the pots on my hotbar, clicked, and (you guessed it) ....
Curious, I went into a quest instance and tried to damage a "foe". Same thing.(Combat): You attempt to save versus inflict serious wounds. You roll a 15 (+52): save!
(Combat): You suffer 12 points of damage from Inflict Serious Wounds.
I'd assume that these are just for Pale Master self-healing, but why not just say that on the spell description?