Necrosis

The flow and conversion of dzenmisa is responsible for all movement in Aiaos, but since the breaking of the original Divine Harmony of the World, that process is imperfect.
Energy of many forms pool in the World, but some energy then festers. This decaying energy is called necrosis, and has dominion over other decaying things. When it is allowed to build up around dead things, it can impart an unnatural animation to flesh, bone or spirit.
In the hands of a spell caster, necrosis can be used to animate or control the dead, or to rot and corrode physical things, and is the heart of the study and school of necromancy. Many cultures frown on the practice of necromancy and the use of necrosis, seeing it as a violation of the natural order. Necromancers insist that others simply fear death and do not want to be forced to think about it.
The most feared and reviled consequence of necrosis is the existence of the undead; any creature that is suspended by Magic in an animate, but unliving form. Said magic may be a deliberate working, or it may result from a quasi-natural accumulation of necrosis. The first and greatest such accumulation, and the first centre of necromantic study, was in the titanic necropolis of Thosis.