Polymorph

Polymorph refers to the magic that changes one creature into a different species. It can also change an object to another object of the same type. (Someone please clarify what happens to objects if they are in the inventory of you or the monster while you or it polymorphs.)

Several things can polymorph you, monsters, or objects:
 * ring of polymorph
 * spellbook of polymorph
 * wand of polymorph
 * polymorph trap

&rarr; Polypiling is the practice of aiming polymorph at a pile of junk, hoping to produce better or rare items.

&rarr; Polymerge combines stacks of items into golems.

Monster versus adventurer polymorphs
NetHack treats the situation differently depending on whether you (as the adventurer) or a monster polymorphs.

When a monster polymorphs, the change is permanent. For example, if you change your pet dog into a dragon, it will never become a dog again (except by chance from a later polymorph).

If you polymorph, the change is temporary; you will eventually return to your old form. The polymorph will time out. If your health reaches zero while polymorphed, you will also return to your old form instead of dying.

An interesting case of this is lycanthropy. If you have this condition, you will sometimes polymorph into a canine (a jackal, for example). There is also a monster in the game called a werejackal, which in its human form will also sometimes become a jackal. As the jackal, either you or the monster can summon allied jackals as help. (If you summon them, then you keep the jackals as pets.) The similarity ends when as the jackal, you or the monster lose all of your health. You will become your normal race again, while the monster will die without transforming back into a human.

SLASH'EM changes the behavior from vanilla NetHack. In SLASH'EM, monster polymorphs behave more like player polymorphs in that monsters who are killed while polymorphed will revert to their original form.