Bowser's Dark Matter Plant

Bowser's Dark Matter Plant is a Bowser galaxy in Super Mario Galaxy. This galaxy has a huge gravity-flipping area, along with lots of patches of Dark Matter, which is deadly to the touch. Bowser is fought at the end; the fight is much tougher than the previous one. If Mario wins, he receives a Grand Star.

Darkness on the Horizon
Mario and Luigi must go through the plant (including a side-scrolling area), avoiding black holes and Dark Matter and the holes it burns into the ground. Eventually he will reach Bowser who must be defeated the same way he was last time.