Heroic Map Pack
The Heroic Map Pack is the first map pack released for Halo 3.
It includes three maps: Standoff, Rat's Nest, and Foundry. It was released at 2:03 AM on December 11, 2007, originally available for 800 Microsoft Points exclusively on Xbox LIVE Marketplace. Each map presents a totally different play style. There are a handful of new Forge items usable on these maps that were just static parts of the environment on previous maps. These items range from shield walls to man-cannons, to other novelty objects, such as large soccer balls.
- Main article: Standoff
The symmetrical valley of Standoff, with its entrenched bases, fields of boulders and open driving spaces, is ideal for mid-sized objective and Slayer game types. There is a secret forge item for this map. Standoff (as well as Valhalla) is considered by some the successor to Halo's Blood Gulch. Standoff was codenamed Jodrell Bank.
 Rat's Nest
- Main article: 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 and its symmetrical design makes it perfect for strategy-based games. Rat's Nest was codenamed John Carpenter's Prince of Dorkness.
- Main article: Foundry
Foundry is a Forge based 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. Foundry was codenamed Art Vandelay, which is a reference to the TV show Seinfeld.
There was a three-part trailer called "D.I.Y", which was hosted by the members of Red vs Blue that showed a preview of the maps in the map pack.