- The Thirteenth Legion is a group of Autobots in the cartoon portion of the Generation One continuity family.
The Thirteenth Legion (also known as the Lost Legion) was an ancient group of Autobots that abandoned Cybertron after the wars that consumed the planet. They settled on the planet Antilla where they formed a thriving community with advanced technology.
The colony continued peacefully for some time until an asteroid shower impacted the planet and infected the Autobot colonists with Cosmic Rust. Unable to discover a cure despite their advanced technology, the colonists all died. Cosmic Rust
The written language of Antilla is Ancient Autobot, a dialect no longer understood by modern Transformers. This, (combined with other factors) places the Thirteenth Legion's break with Cybertron between 11 million years ago and 9 million years ago.