Galleom is a boss that is encountered twice in The Subspace Emissary.
Galleom appears to be a giant, purple robot. It is covered head to toe in a heavy Mech arsenal, possessing two rocket launchers as shoulder weapons. It wears an iron knight mask that covers its face, and metallic arm braces over its bulky forearms. It has skinny (compared to the size of its body) robotic legs.
Galleom can transform into its Tank Form, in which its head and feet retract to meet with the body, and its arms fold backwards to form wheels. The shoulder rocket launchers then lock into a fixed state facing the opponent. Its head contains a Subspace Bomb.
Role in the Subspace Emissary
It is first seen by Marth, Ike and Meta Knight, traveling through a desert in its tank form. After its first defeat, it crashes through the ground and lands in an underground temple, where it must again be fought by Lucas and Pokemon Trainer. After its second defeat, it tries to detonate a Subspace Bomb, but ultimately destroys only itself (although it does absorb the trophy of Wario in the blast). It is reconstructed by Tabuu to attack the heroes in the maze he creates.