Carbuncle is a Cocoon fal'Cie in Final Fantasy XIII. Located in the Nutriculture Complex underneath Palumpolum, it is responsible for the city's food supply. Carbuncle is a large floating crystal with butterfly-like wings adorned with two faces similar to the ones adorning Barthandelus. Its shape takes elements from Lindzei's crest.
Carbuncle is a Sanctum fal'Cie charged with food production. Stationed in Palumpolum's subterranean nutriculture complex, this fal'Cie oversees a process of ultra-efficient hydroponic farming employing mobile paddies and careful regulation of light and water.
A parallel process within the facility generates raw protein to supplement the vegetable foodstuff produced.
Hope shows Lightning the fal'Cie Carbuncle, with the latter wondering if they should attack it and thus destroy Cocoon's source of nourishment. Hope says they should leave it, since they do not want another reason for everyone to hate them.
Like many of the fal'Cie, Carbuncle is named after a recurring summon in the series. Carbuncle was a mythical creature reportedly sighted in the Americas by Spanish conquistadors. It is described as a small creature, either a bird or a mammal, that has a gem in its forehead crystallized from the brain of a dead dragon. According to myth, it is good luck to catch a carbuncle. A carbuncle is also an archaic name given to any red cabochon cut gemstone. The name applied particularly to red garnet.
- Although it bears no visible similarity to the common summon of the series, it was assumed Carbuncle would make an appearance after it was revealed in teaser trailers. Carbuncle Eidolon appears in part of the Pompa Sancta parade with a design of previous incarnations of Carbuncle. The Carbuncle is a Nautilus mascot and thus a popular plush toy. One appears in Palumpolum when Snow and Hope have a run in with an anti-l'Cie mob; Hope tries to help a girl and she throws her toy Carbuncle at him. After Snow separates them from the crowd, Hope picks up the doll, placing it on the debris and apologizes.
- A model for Carbuncle exists in the game disc of Final Fantasy XIII-2, although it never appears in the game, making it dummied content.
- The fal'cie's "core" is that of a ruby, giving it the same trademark as its mythical Eidolon counterpart.