A Corpseborne is a powerful form of Great Existence, the owner of a Black Ring and the core of its contamination. When a Black Ring descends, its Corpus may construct a monstrous body out of the bodies of Corruptors and other Manic entities. This body then surrounds the Corpus's core, a bubble of red flesh. Inside the core is a black hole, which contains the same withered human figure seen within the Inheritance. Inside its Black Ring, a Corpseborne is protected by a veil that rejects all attacks, which is capable even of defending against the Rules.
Due to a small sample size, the abilities of a Corpseborne are unclear. The Corpseborne of BR-002 is able to leave its Black Ring and survived for years outside of it, even after having been cut in half, although the second half of its body remained within the Ring. It also was notable as the most cunning and secretive Great Existence yet encountered by the MBCC, able to spread its contamination without detection over long periods of time. However, any or all of its unusual properties may be due to its unique bifurcated existence. Although the Mania crisis in the unclaimed crypt was resolved and the Inheritance defeated before a Black Ring appeared, the "Skeletal Mutant" enemy that emerged from the sarcophagus after it consumed numerous Maniacs is listed as a Corspeborne-type enemy, suggesting that a Corpseborne may be possible even outside of a full Black Ring.
One commonality among Corpsebornes may be an obsession with longevity and survival. The Corpseborne of BR-004 says that once it has descended, it is meant to live eternally, and the Corpesborne of BR-002 is single-mindedly obsessed with ensuring its own survival even after being cut in two.
In the game's original Chinese, the name of this entity is "受骸者", meaning "one who bears the corpse". The character meaning corpse, "骸", is the same character that is translated as Corpus.