Heroic Map Pack

The Heroic Map Pack was announced on November 19, 2007. It includes three new maps, Standoff, Rat's Nest, and Foundry. It will be released on December 11, 2007. Available for 800 Microsoft Points exclusively on Xbox live Marketplace, each map presents a totally different play style. In spring 2008, it will be released for free, right before the next wave of Halo 3 maps. A member of bungie staff has said that in 1 or more of these maps you will be able to add a man cannon on forge.

Standoff
The symmetrical valley of Standoff, with its entrenched bases and fields of boulders is ideal for mid-sized objective and Slayer game types.It has also been said by bungie staff members that there is a secret forge item for this map.

Rat's Nest
The vast, labyrinthine passages of the Rat's Nest bring something completely new to the multiplayer experience: an indoor vehicle paradise. Strongly influenced by the Campaign level Crow's Nest, this map is ideal for big team battles. Bungie has stated you can have a scorpion indoors on this level.

Foundry
Foundry is 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.