The five Buuthandi are the primary habitats of the F'sherl-Ganni Gatekeepers. They resemble Dyson spheres, but are a different concept; while a Dyson sphere is a rigid shell, a buuthandi is essentially a giant balloon of solar-sail material, with space stations, habitats, and ballast hanging from the inside surface. Due to their construction, their deck gravity is probably either the very light solar gravity, or gravy-based.
Each of the buuthandi stars has a wormgate in its core to supply mass for the duplicator wormgates that keep the population fed and supplied.
There used to be six buuthandi, but one was wrecked by Admiral Breya's coalition fleet in the famous Battle of the Buuthandi. Of the remains, the gate-clone prisoners were rescued by the fleet, the habitation modules not used as shields by the fleet escaped into interstellar space, and the star was blown up with a T'okjith.
The word buuthandi comes from the F'sherl-Ganni phrase "Buut go buut-buut nnaa-nnaa cho handi", which translates roughly as "this was expensive to build."