On December 11, you can dwnload The Heroic Map Pack From the Xbox Live Marketplace for 800 Microsoft Points. The download contains 3 new maps:
This map has entrenched bases and fields of boulders that make it ideal for mid-sized objective and Slayer game types.
This map brings something completely new to the multiplayer experience: an indoor vehicle paradise. Strongly influenced by the Campaign mode, this map is ideal for big team battles.
The ultimate Forge map. Players can edit every single object in this voluminous industrial warehouse, placing stairways, walls, bridges, and tunnels to create an entirely new play space and build almost any kind of map imaginable.
All three maps will become available for free download via Xbox LIVE Marketplace in Spring 2008, just prior to the next wave of new Halo 3 multiplayer maps.