Porkalator
Porkalator is a monsters-only spell which attempts to temporarily turn the target into a hog. This target is probably going to be you. This will meld your armour, weapon, and rings into your body, suppress suppressible mutations, and prevent you from casting spells until it wears off.
As with any other non-damaging enchantment, high magic resistance will help you to avoid becoming porkalated.
Only natural, demonic, or holy creatures can be affected by this spell (so you're safe if you're undead or in lichform). Demonic creatures will be turned into hell hogs, while holy creatures become holy swine. Note that this does not include you (e.g. demonspawn and demigod characters will still become average hogs).
The following monsters can cast Porkalator: