An Abnormality from Project Moon's works (Lobotomy Corporation, Library of Ruina, Limbus Company), appearing in Lobotomy and Library as of 01 Apr 2025.

Big Bird is a large black bird-like creature carrying a lantern and possessing a multitude of eyes, and is closely tied to two similar avian Abnormalities, Punishing/Small Bird and Judgement Bird. In Lobotomy it is classified as a WAW (second-highest on the game's threat scale) and the three birds can combine into another Abnormality called Apocalypse Bird; in Library they are associated with the Binah floor and are fought both as individual Abnormalities and as part of the floor's Realisation boss fight.