RWBY: Beacon Academy
Geists are a species of Grimm resembling a ghost and capable of "possessing" inanimate objects. A Geist's base form is covered in bone-like spines with long, skeleton-like forearms and sharp fingernails. Due to it's ghostly appearance, it lacks a lower body, instead floating through the air while leaving behind a black smoke trail. Its face consists of Grimm markings on a bone plate with a single eye.
A Geist is a possession-type Grimm, capable of controlling any inanimate object it possesses as extensions of its own body. Should it lose any of its possessed limbs, it can repair the chink in its armor almost immediately by simply possessing another object in the vicinity. Its only real vulnerability is its "face", the central segment from which it maintains control of the form as a whole. All of its limbs must be destroyed at once in order to expose this vulnerability. A Geist's possessed body, however, are virtually immune to melee and ranged attacks, as well as dust-enhanced elemental strikes.
While possessing inanimate objects as a body, a Geist's limbs are not connected physically to one another and are held together by an invisible force that seems to have no difficulty moving massive objects. Most of a Geist's attacks utilize it's enormous mass and size in brute-force attacks, though they have displayed the ability to use discarded pieces of its body as projectiles.
Once the host object is destroyed or severely disabled, it abandons the body, revealing its base form. There are no records of a Geist demonstrating any combat abilities in this form, and is relatively frail. A Geist in its base form can easily be dispatched from a single attack.