Bowser's Dark Matter Plant

Bowser's Dark Matter Planet is a galaxy featured in Super Mario Galaxy. It is the boss galaxy of the fourth world, which is accessible from the Comet Observatory's Bedroom. As its name suggests, Dark Matter is prevalent as the galaxy's prime enemy.

Mario can access this galaxy if he has 33 Power Stars in his possession, including the Grand Stars from Bowser Jr.'s Robot Reactor, Bowser's Star Reactor, and Bowser Jr.'s Airship Armada.