Caldoon 4

Caldoon 4, or Caldoon IV, is a planet in the Caldoon System, and was the site of a battle a long time ago.

IDW Generation 1 continuity
Caldoon 4 was the site of a battle between Overlord and a group of Autobot soldiers. Kup was in this group, and he was almost defeated by Overlord, when Overlord flew off to attend a holoconference with Megatron, Sixshot and Black Shadow. Megatron informed Overlord and the others that they would be his phase-sixers. Overlord said he had other ambitions, and Megatron told him that if he followed those ambitions, he would be destroyed. Overlord went back to the fight, but he flew off, sparing Kup's life again.

The AllSpark Almanac
Caldoon IV was a neutral robotic planet in the Milky Way.