Brimstone of Accelerated Decay

Wondrous item, uncommon

This small crystal is composed of pure Sulphur, unlike usual ore. When placed within 2 feet of a corpse of any creature except Celestials, Fiends, or Undead, the crystal speeds up its decay tenfold. This may take place as erosion in an Earth Elemental, Rot of Fungal Blooms in flesh-based creatures, or rust in Constructs.

Whatever the case, when all that is left are bones or a sufficiently small volume, the item's effect ceases.