Gathaghast's Onomastic Rot

Gathaghast's Onomastic Rot is an 11th-level spell that somehow afflicts creatures that have trunames with a vile curse when they falsely give the truname of another necromancer. It was cast by Gathaghast in 320 GR. When a necromancer attempts (and fails) to cheat a proper authentication ritual, they are subject to this effect. In short, it causes the victim's flesh to rot off. The flesh becomes a pile of noxious-smelling, black goo. On those without flesh, including those that survive the process, it has quite the different effect - it causes their magic to rot, causing them to permanently lose spell levels continuously once a day. Once they run out of spell levels, they are instantly transformed into a ghost. Only a wish (or stronger) spell or death can prevent this process, and a victim killed before the curse finishes is instantly drained of spell levels and still rises as ghost. Any creature afflicted with the curse is instantly stricken from the Metaphysical Book of TruNames.