Bowser Jr.'s Lava Reactor

Bowser Jr.'s Lava Reactor is a galaxy in Super Mario Galaxy. This is where Mario battles King Kaliente once again and receives a Grand Star. The galaxy is one extremely large planet made completely out of lava with very few rocks.

King Kaliente's Spicy Return
Mario lands on a small planet with a few Goombas, a Bullet Bill cannon, and a caged Launch Star. Mario will have to lure a Bullet Bill to the cage to smash it open, gaining access to the Launch Star. The Launch Star shoots him the Lava Reactor's surface, which is entirely lava, except for a few platforms. Mario will encounter two brown Electrogoombas that Mario will have to defeat to get another Launch Star. From there, Mario will go on to fight a very strong version of King Kaliente. Upon defeating him for the second time, he will receive the sixth Grand Star.