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 Bullit Bill to the cage to smash it to gain 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 enemies that fire fireballs and rocks at him, which 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 recieve the fifth Grand Star.