From Lexicanum

The Hemlock is an Eldar space vessel. It is a very simple design, consisting of a powerful pulsar lance and an engine, and little else. It is more of a flying gun than a ship proper. It is likely that the crew numbers are small, the interior power requirements for maintaining an atmosphere would take so much energy as to prevent the use of the warp drive or main weaponry. This makes them easy prey for boarding actions.¹

Sources

• ¹:Battlefleet Gothic Rulebook p133