Microsoft has begun promoting Halo 3 with a viral marketing campaign that promises to reveal more about the game's universe and backstory.
Speaking to our sister site, Eurogamer.net, a spokesperson said that the campaign is titled 'Iris' and will run for several weeks.
"'Iris' is a spiral campaign designed to take gamers on an incredible journey through the Halo universe," he stated.
"Led by an 'unknown' hand, users will discover bits of previously unknown information about the Halos, the Flood, the Forerunners, and the true origins behind the Halo trilogy."
Bungie content specialist Frank O'Connor has written most of the material, with help from community manager Brian Jarrard and artist Aaron LeMay.
The campaign kicked off this weekend when groups from an organisation called The Society of the Ancients took to the streets of cities such as New York and London to hand out flyers with the message, "We are not alone."
Microsoft also used a viral campaign, ilovebees, to promote the second Halo game, and launched a similar initiative - origen - in the run-up to the debut of Xbox 360.
Halo 3 will launch on September 26.