Assembly

Assembly is the official name for the map that was announced in the Bungie Weekly Update (8/22/2008). It was originally planned to be in the Legendary Map Pack, but was replaced by Blackout due to the fear that it wouldn't be finished on time. At the current time there is no known release date for this map.

This Covenant themed map is a symmetrical battleground, not too unlike Midship but a bit larger. With the middle of the map being lower than the rest. It is supposed to be full of mid to long range weapons, and it appears there will be multiple floors. This map is most likely based within a Covenant ship, factory, or some other structure.

Design
Due to the name, possible origin, and structure of the level, some fans have speculated that this map will be set on a structure of Covenant origins, with the map possibly taking place on a space station like the Unyielding Hierophant or ship like Pious Inquisitor. According to the Bungie Weekly Update, this is going to be a brand-new map, squashing rumors that Purple Reign (the map's original name) might be a remake of Halo 2's multi-player map, Midship.

It is said to be nearly perfectly symmetrical, with the mid section being higher than the rest of the map. It is also said that it based outside with "some excellent line of sight and well thought-out vertical problems and opportunities ".

The map is focused on competitive playing, as it is multi-story arena-style map. It features two "somewhat enclosed" bases, with one-way mirrors on the second floor (like those in interrogation rooms), where players will be able to look out, but players outside will be unable to see in.

The arena is designed like a bowl, with the floor slightly concave and dotted with columns for cover. Four elevated walkways converge in a small bi-level center structure that sports a cache of important items.

Mystery
Before Assembly was removed from the Legendary Map pack, it was stated that one of the maps would expand upon the Scarab-Hunter mystery. In a recent Weekly Update, it was stated that, "One base of this open-air arena could end up getting called 'Energy side' and another call-out could end up 'Hunter side'", so it's possible that this was the map they were referring to. Adding to this mystery, Luke Smith stated on a thread on the Bungie forums that "the name Assembly is extremely appropriate." This could possibly mean the map takes place on a Covenant factory where Scarabs are assembled or maybe just a reference to the Hunters' scientific name. Of course no one knows for sure.

Trivia

 * The former name of the map, Purple Reign, could been a homonym with the TNT firework "purple rain", it could also be linked as a tongue in cheek reference to the song "Purple Rain" from the artist Prince, but it is most likely to referring to the dominance of the color purple on the map.
 * A screenshot has been found in a NY Times blog that some thought was a Bungie employee working on a 3D model of Purple Reign, however, some people think that the structure is, in fact, a structure from High Charity and can be found on the Halo 2 levels Gravemind and High Charity. This would also fall into the scheme of the in-production name resembling the look of the level, while as the real name represents gameplay.
 * Assembly was first announced to be part of the Heroic Map Pack (while at that time it was called Purple Reign instead), which was soon replaced by Foundry, and then announced to be part of the Legendary Map Pack, but replaced by Blackout, which shows that this map project has been going on for quite a while in Bungie. This long delay of release may possibly mean that the map is currently finished or may be very close to being finished.
 * Although not a true screenshot, a pen rendering of the map was featured in the Bungie Weekly Update on July 25, 2008.
 * This map may be released with Space Camp in the next map pack.
 * Due to the color purple normally associated with Covenant set pieces, has caused fans to speculate a number of rumors about its location:
 * An unseen part of High Charity, before Gravemind infected High Charity and took control.
 * It was believed to a remake of Halo 2's Midship or Gemini but Bungie later stated that this map is not a remake, debunking that rumor.
 * It was rumored that the map would be set on a Scarab or large mobile Covenant base. The pen drawing, shows a possible outline of the legs of a scarab in the top left corner of the picture.
 * In the rendering there appears to be a Teleporter or a Grav Lift, suggesting that this map may have Teleporters or/and Grav Lifts to get around the map.
 * Assembly will be shown and playable for the first time at the Penny Arcade Expo.
 * Due to its name "Assembly" and its possible connections to the Scarab-Hunter mystery, this map may publish Scarabs being build on an assembly line.
 * The map was originally intended for Slayer based games, but objective games are described as playable and frantic.
 * Assembly is the second Covenant-themed map in Halo 3.
 * If you manage to make it to the PAX gamers convention in Seattle WA you will be able to play Assembly before it comes out as DLC on Xbox Live.