Dr. Mallard's Diary: Entry 13

Regarding the nomenclature I use to refer to various types of undead, there is a particular distinction I would like to clarify—-the difference between a revenant and an apparition. This distinction is important as it represents the two major classifications within the hierarchies of the undead. 

A Revenant refers to any being forcefully maintaining a physical manifestation within the material world. It need not be humanoid or even fully organic. It need only have a body, and a ceaseless hunger for a specific material required to maintain its form. A prominent example of this is a ghoul, which consumes rotten flesh in order to subsist.

An Apparition is a general term regarding the spirits  manifesting visible phenomena. While typically attributed to the deceased, it can refer to  many spiritual beings. In contrast to the revenant's constant maintenance of their physical forms, an apparition requires no maintenance. It is incidental to their existence and quite frankly its bane. An apparition always has an anchor of some sort, maintaining their existence on this plane and allowing for their manifestation. This anchor can be either physical or metaphysical. The study of apparition is quite difficult as their abilities and weaknesses wildly vary from case to case, to the point that specific classification would be akin to naming each grain of sand in a desert. Instead, the general rule of thumb regarding the study and management of apparitions is solely classified through general power level,  based upon range and affected objects.