Giant Owls seen in an early version of the elevator scene.
Giant Owls are monsters seen in their cube cells but not during the purge. However, during the second wave of security's massacre, a hooting noise can be heard, meaning that they may have been released and killed one of the guards, but it is unknown how they did it.
Appearance and Characteristics
They are depicted as normal white owls but of abnormal size. The cube with the white owl is duplicated.
An owl statue summons it if you tamper with it.
Inspiration
The owls could be a gag monster, in line with the other "Giant X" animal entries. It's also possible the white owl is a reference to the Goblin King in Jim Henson's Labyrinth.