Phantom Fleet

When a flotilla of Worldsweeper-class warships disappeared, the Decepticons memorialized them as the Phantom Fleet.

Fiction

IDW Generation 1 continuity

At some point during the Great War — likely before the fall of the Decepticon Constellate that saw the "symbol ships" rendered obsolete — a group of Worldsweepers went missing while passing through the Dark Nebula. Anomie

Centuries later, the enigmatic Grand Architect and his affiliates were known to make extensive use of Worldsweepers, long after they had fallen out of use... Chasing The Infinite