The Keyship is a classification of supra-luminal Forerunner naval vessel in use at the time of the Forerunner-Flood war. Mentioned in the hidden Terminals found on the Ark and Installation 04B, Keyships were a class of Forerunner vessel capable of activating portals leading to the Ark. They were capable of remote detonation to prevent their usage by the Flood. Though many more once existed, the majority were destroyed by the Librarian to prevent the Flood from reaching the Ark.