Erumpent horn
The horn of an Erumpent, holding a fluid that makes anything injected with it explode.
An Erumpent horn is exactly what its name says, and it is dangerous to keep: the horn holds a fluid that makes whatever it is injected into explode. That property makes it prized as a potion ingredient and awkward as a possession, and it is listed as a Class B Tradeable Material, which limits who may buy and sell one. Some people keep them for decoration regardless. After a run of caravans blowing up in transit, the International Magical Trading Standards Body published a paper establishing that a ground horn is far less volatile to move than a whole one.
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