Petitioner
Whilst the term "Petitioner" is a legitimate old-timey term that basically means "a person asking a figure of authority for a favor", it has a more specific use in Dungeons & Dragons and thus on /tg/. Introduced in the Planescape setting, Petitioners are the lowliest form of Outer Planar life, representing the spirits of the deceased in their respective afterlives scattered throughout the multiverse.
Now, the specifics of things like appearance vary depending between the planes, but the basic concept remains constant. Petitioners don't really remember their mortal lives all that well, and basically exist to carry out an existence based around their specific planar location - depending on where the sods ended up, this will ultimately end at some point with either their transformation into a true planar being, such as a fiend or an angel, or their total subsumption into the essence of the plane itself.