With more than 27 million copies of Halo games sold worldwide, Microsoft hopes that its new Halo 3: ODST for the Xbox 360 will be selling as well as its predecessors.

Click to enlarge

According to Microsoft, players will now have the opportunity to take a step back in time and experience the “Halo” universe from a whole new perspective. Players must search for clues to find out what happened to their squad when a drop into the city of New Mombasa goes wrong, and discover the secret behind the Covenant’s interest in the city.

In addition to a full-fledged campaign, “Halo 3: ODST” introduces Firefight, a new cooperative multiplayer mode where up to four players battle waves of unrelenting Covenant onslaughts. The game also introduces three new “Halo 3” competitive multiplayer maps and contains the complete, standalone “Halo 3” multiplayer experience on a second disc. “Halo 3: ODST” will also act as a key to entry into the “Halo: Reach” multiplayer beta at a later date.

The “Halo” franchise is an award-winning collection of properties that have grown into a global entertainment phenomenon. Beginning with the original “Halo: Combat Evolved” for Xbox in 2001, the rich fiction of the franchise has since inspired a series of blockbuster Xbox and Xbox 360 video games, New York Times best-selling novels, comic books, action figures, apparel and more.

“Halo 3: ODST” has a recommended retail price of $99.95 and is rated “M” for Mature audiences. Customers buying an Xbox 360 Elite from today through to October 20, 2009 will receive a Halo 3: ODST for free.