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 must go through the plant (including a side-scrolling area), avoiding 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.