Corpse Wax

Corpse Wax is a reagent.

Source
Corpse was can be found on undead throughout the Hidden Vale, but is most common in the ruins of Ravensmoor.

Trivia

 * During Release 7, ectoplasmic residue could occasionally be found. This was replaced by corpse wax, as the former name was not "gameworld compliant", likely due to the Ectoplasm reagent.
 * During Release 12 due to some pranks with Corpse wax bought at vendors, Lord Enmar is no longer accepting Corpse wax as proof of slaying undeads.