Guardians are a fortress-class Beast ship. Though not nearly as large as a Blue Flower, they are still massive compared to warships. Extensively fitted with both Jamil Organs that extend a perfect ECM over communicating radars as well as with Chamild Organs that distort visible light and controls the visibility, these special fortresses stay in the stratosphere and effectively isolate an entire planet from space.  They can also store many ships.
Appears in ME0-Ch13.