The Codex is an alien who is a contestant in the seventh Presidian during Contest.
The Codex are black-colored aliens, with a floating triangular head, and a body and tail of trailing spheres. It moves by silently hovering through the air, and attempts to strangle its prey.
The Codex was teleported into the New York Public Library to partake in the Presidian and would later find Paul Hawkins and Balthazar holding up in a storage facility. The Codex attacks and Hawkins sets fire to the room, hoping to stop the Codex, which fails. Balthazar however tells Hawkins to flee while he deals with the Codex. When the facility explodes, Hawkins who just managed to escape, sees the Codex stumble out of the room before collapsing, dead.