Dark Matter Thieves

The Dark Matter Thieves (暗黒盗賊団ダークマター, Ankokutōzokudan Dākumatā) are a group of alien invaders led by the powerful Lord Boros that attacked various planets to find valid opponents.

Headquarters
The Dark Matter Thieves headquarters is a giant spaceship, so big that it can obscure even A-City. It's heavily armed with cannons able to shoot enormous destructive bullets and is able to fly thanks to a Power Core, the destruction of which makes the spaceship fall almost immediately.

Trivia

 * According to Genos' notes, the size of the Dark Matter Thieves' ship is 9,230m x 15,024m.