Halo 3: ODST

Halo 3: ODST (formerly known as Halo 3: Recon) is a first-person shooter video game developed by Bungie for the Xbox 360. Halo 3: ODST was released worldwide on September 22nd, 2009. The game is effectively the prologue to Halo 3, which fills in the details of what happened in New Mombasa between Halo 2 and Halo 3. While available from the Xbox Live Marketplace for the Xbox One, Halo 3: ODST requires Halo: The Master Chief Collection, and once downloaded, is available for play under the Halo 3 tab on the main menu.

Helljumper
An official five-part prequel comic, Helljumper, was released in the months leading up to and after the release of Halo 3: ODST, starting in July 2009, and ending in November 2009. An Xbox LIVE invitation to the multi-player Beta of Halo: Reach, announced at E3 2009, was included with Halo 3: ODST, and ran from May 3, 2010 through May 20, 2010.