When you engrave with a wand of polymorph and mutate a preexisting engraving into a rumor, the rumor should always be true if the wand is blessed, false if it’s cursed, and random if it’s uncursed.

A game mode that makes you play a Wizard and guarantees you start with a “polyrunner” kit - wand and ring of polymorph and ring of polymorph control. (Maybe also potions of polymorph). This can be startscummed for, but of course takes many games to get this exact kit, so the game mode circumvents this. To balance it out, random objects don’t generate, or generate at a very reduced rate.

Zapping a wand of polymorph at Master skill gives you control over the form the target monsters polymorph into, whether that is yourself or others. Other monsters still get their chance to resist the polymorph entirely.

It would not give you control over what an object would polymorph into, for obvious reasons.

However, if there are monsters that can use the wand of polymorph at master skill, this has the potential to become very annoying very fast, since they would be able to turn the player into a sessile monster, make them break their armor, or turn themselves into something very threatening and out of depth.

When you attempt to polymorph an item that has polymorph magic (wand/spell/potion of polymorph, tin of meat that may cause a polymorph when eaten, etc) it explodes and creates one or more monsters affiliated with polymorph magic, such as polymorph vortices (see YANI #3669), genetic engineers, or similar.