 Alternate reality games were used to promote the release of the games in the main trilogy . The Cortana Letters , a series of cryptic email messages , were circulated by Bungie prior to Halo : Combat Evolved 's release . I Love Bees was used to promote the release of Halo 2 . The game revolved around a website created by 42 Entertainment , commissioned by Microsoft and endorsed by Bungie . Over the course of the game , audio clips were released that eventually formed a complete five @-@ hour story set on Earth between Halo and Halo 2 . Similarly , Iris was used as a viral marketing campaign for the release of Halo 3 . It featured five web servers containing various media files related to the Halo universe . 
