Lithone

Lithone was a planet inhabited by transforming robots whose relationship (if any) to the Transformers of Cybertron is unclear. The inhabitants are known as the Lithones or Lithons.

Unicron ate it.

Cartoon continuity
Lithone was destroyed by Unicron in the year 2005. Two of its inhabitants (Arblus and Kranix) seem to have had prior knowledge of Unicron's existence. The Transformers: The Movie

The AllSpark Almanac
The Lithons shipped medical relief supplies to both sides during the Great War. Years after the war ended, the planet has been destroyed, it is unknown how, fan-known only. Transformers Animated: The AllSpark Almanac II

Super INFINITY
Lithone appeared in Super INFINITY. In Unicron Trilogy, Lithone was destroyed by a awakened Unicron in the year 2005. Two of its inhabitants (Arblus and Kranix) seem to have had prior knowledge of Unicron's existence. Lithone was recreated in Alpha Q's universe.