D2 Field

D2 Fields are a card type that was introduced in DMD-31.

Details
It stands for Dynamite Dangerous Field. This is not a game term however, the pronunciation for the card type is "Di-Tsu Fīrudo".

They are are played from your hand for their mana cost and have an ability while they are in the battle zone. If another D2 field is put into the battle zone, the D2 field that was once there will be put into the graveyard. This includes your opponent's D2 Fields, so beware if your opponent can use D2 fields as he can simply place a D2 Field to remove yours.

Some of them feature an ability known as Denjara Switch, allowing them to turn themselves upside down once a game to trigger an ability.

They can only be removed from the battle zone by Card Removal effects, or by putting another D2 Field into the battle zone.

Story
These are spaces which defy regular logic created during Dokindam X, The Legendary Forbidden's rampage. They are inhabited by Initials, and the stronger ones are guarded by Master Initials

Trivia

 * D2 Field can be considered an equivalent of Magic Field cards in Yu-Gi-Oh! trading card games and Nexus in Battle Spirits.