The Hammer and the Soul
Modified Mercy-class Prison Ship
A relatively tiny vessel, primarily designed for the securing and transport of prisoners. The standard model can house up to 2,000 live prisoners or 10,000 in cold storage. However, those readied in preparation for the Black Ships have been modified to carry psykers exclusively; the space required for the psy dampeners, additional engines, and sheer prudence (in light of the dangerous cargo) limits each vessel to fitting only 100 psykers.
20 such ships make up the prison fleet which awaits the Black Ships.