Extremely bizarre question for GMing purposes! I need an expendable magic item of some kind, not a potion/scroll/wand but ideally of the "becomes a mundane item when used up" variety, that turns people into things, even if just partly. Like, growing claws or changing size or something would suffice. But the more dramatic, the better. Bonus points if it's the kind of item someone might keep around without knowing about it being magical.
It looks to me that it can be some kind of wondrous item, slotless would probably work the best. Constant magic aura can hide its magical abilities. Automatic activation when specific condition is met.
There are multiple wondrous items those that are one-use only or have a limited number of uses, maybe you can use one of them as a basic for whatever you need.