The Secret Marine on The Covenant is a Marine hidden in a hard-to-access location in the Halo 3 Campaign level The Covenant. The Marine only appears on single-player Local Play, and can be accessed using a Ghost or a Prowler. Sometimes, two or more Marines will appear. It is suspected that the faster you get to the Marine, the more Marines you will find. There appears to be a kind of time limit after which the Marine will not be present—whether he disappears or heads to another location is unknown. Once you encounter him, though, he will never leave his position.