Thrull

Thrull was the planet that Galvatron ended up on after being thrown out of Unicron's body. It orbits the red giant star, Hydran.

The Transformers cartoon
Spending such a long time buried in one of Thrull's pools of lava plasma severely damaged Galvatron's mind, driving him stark-raving mad.

After learning his location from Unicron's databanks and collecting some Energon cubes from their fellow Decepticons, Cyclonus and Scourge went to rescue their master from his imprisonment. Five Faces of Darkness, Part 1  After violently attacking his own troops for attempting to steal him away from his "kingdom of desolation", Galvatron left Thrull, but not before he could destroy the planet for no reason at all while cackling wildly.Five Faces of Darkness, Part 2

Galvatron's pretty crazy.