The Unlimited Neutral Field (無制限·中立·フィールド, Museigen Chūritsu Fīrudo) is an environment a Burst Linker can enter by using the "Unlimited Burst" command. In order to enter the field, the Burst Linker must be at least level 4, and executing the command costs ten Burst Points.
The Unlimited Neutral Field is a zone encompassing the entire Accelerated World, but unlike the normal duel environment, it has no requirements on what to do when there. Burst Linkers are free to fight others, or NPCs known as Enemies, as they so desire.
Like the normal duel environment, the entirety of the world is based on the real world as it is seen through the Social Camera Network, "skinned" with a semi-random Stage. The process of the Stage changing is known as a Transition. During a Transition, the environment is completely reset, and any Enemies that were destroyed are reborn.
All across the world there are places known as Leave Points, or Portals, that allow a Burst Linker to exit from the Unlimited Neutral Field. There is no other way to leave, besides physically removing a cable from a proxy server connected to the Global Net. These Portals are indestructible objects, and cannot be moved at all.
While in the Unlimited Neutral Field, Burst Linkers will feel the full amount of pain from their actions, rather than only half of it like they do in normal Duels.
Metatron's second form refers to the Unlimited Neutral Field as the Mean Level, while she and Silver Crow are on the Highest Level. Earlier, she had referred to the Normal Duel Field as the lowest level.
Various kinds of enemies can be found all across the world. There are four classes of Enemies, ranked by power:
The Unlimited Neutral Field is also host to various dungeons. The most important of these are the Four Great Dungeons. To clear each of these requires a large party and a lot of combat experience. The last boss of the four dungeons are referred to as the Four Divinities, and the first to win has the privilege of acquiring one of the Seven Arcs.
- Shinjuku Metropolitan Building Dungeon (The Impulse)
- Tokyo Station Underground Dungeon (The Tempest)
- Tokyo Dome Dungeon (The Strife)
- Great Shiba Park Labyrinth (The Luminary)
The Imperial Castle sits in the middle of the Tokyo metropolitan area, in the Chiyoda region, and is considered to be a dungeon. However, only a select few Burst Linkers have ever made it inside - and those due to coincidences or freak occurrences - because of the castle's four guardians, the Four Gods: Suzaku, Byakko, Genbu, and Seiryuu. Each of these Enemies guards one of the castle's four gates, and represent the four compass directions.
While not technically a part of the Unlimited Neutral Field per se, Legions may own territory across the Tokyo metropolitan area. The area is separated into a few dozen Areas, and a Legion may occupy it and defend it from invaders. In addition, Burst Linkers currently in the real world in their own territory cannot be pulled into a duel via challenge.
Control over Areas is decided via Territory Battles, which occur every Saturday. In order to defend an Area, members of the Legion must achieve at least a 50% win rate in a series of team duels based on capturing points.