The Doom Dimension is an alternate dimension from the real world, possibly also in New Vestroia. It is a location in the Bakugan universe. It is known that no Bakugan has ever returned from there until the Brawlers and their Bakugan were released from here by the Legendary Soldiers.
Masquerade and Hal-G presumably made Doom Cards and distributed them, which, when set, send the opponents' Bakugan into the Doom Dimension when they are defeated. All Bakugan are afraid of the Doom Dimension. Hal-G has made a teleportation card that can to teleport a person into the Doom Dimension. The Doom Dimension is said to be the afterlife for Bakugan. It played a main role in the first season.
The Doom Dimension also takes part in Arc 2 of Bakugan: Mechtanium Surge. A mysterious man named Wiseman freed some Bakugan from the Doom Dimension who called themselves Nonet Bakugan.
In the Bakugan videogame, Leonidas and Vladitor are born from the Doom Dimension and released into the human world. Later they both battle and after the battle they both go back to the Doom Dimension, where Battle Ax Vladitor gives Omega Leonidas his remaining energy so he can go back to the human world with his partner (you) but somehow Marduk (your rival) still has Battle Ax Vladitor.