Katratzi was a secret, hidden, moon-sized Scarran base, nestled in Scarran space, occasionally rumored to exist, but not confirmed until the crew of Moya found evidence of it. It had been described as the seat of Scarran power, fortified and dangerous. It disguised its presence by mirroring the orbit of one of the moons of planet Trelast. Katratzi was only reachable by means of a gateway station into Scarran space and depending on whether one is going willingly or not, one may never leave once they get there.
It is possible that the name "Katratzi" was based on real-life prison Alcatraz.