The Brotherhood was first spotted in the Looniverse during Infinite April, when the Xinerama Brother from sci.physics.plutonium came to warn Cannon Fodder of an attack by the Brotherhood upon the Looniverse. Later, that Brother returned, but was killed by another Brother, who attempted to destroy the Looniverse with the Ultimate Gnab.
For the many months of Infinite April, Cannon Fodder searched for the Xinerama's home newsgroup. Finally, he found it, and used the Ultimate Gnab to collapse not one but two universes on top of them, destroying them utterly.
Each member of the Brotherhood is identical. They have deep, reflective black skin, like a deactivated LCD screen. Three thick strands, red, blue, and green, run from their eyebrows to the back of their necks. Their eyes are red, and they have sideburns, which are green on the right side and blue on the left. They wear strange, ceremonial armor.
Their name is derived from the Unix extension that allows a desktop to stretch over multiple monito— er, displays. Screens, if you will.