Halo 3 Epsilon

From Halopedia, the Halo wiki

A Gamercard demonstrating one of the first players of Halo 3 Epsilon.

Halo 3 Epsilon[1] is an internal-only Halo 3 build.

It was released to Microsoft employees as of August 10, 2007, and featured campaign (single-player and cooperative gameplay both), Forge, and multiplayer modes[2][3].

Halo 3 Epsilon was confirmed to some degree later on August 10th by Bungie Studios on a Bungie Podcast. Microsoft employees, Xbox.com representatives, and the Bungie Studios staff have been playing it, and Bungie employees are using this build to finish the final details of the game.

References