The Shroud is an especially stealthy vessel. Its hull is a refinement of the normal necron design, which is even harder to detect. The complete rules for the Necron Fleet can be found in Battlefleet Gothic Armada
The Shroud Class was first recorded in 992.M41 during an engagement with Battlefleet Pacificus. In the six years immediately after, vessels of this configuration were observed on three occasions and each time disengaged before Imperial vessels could bring them under fire. It was believed that either the class or crew were being tested in some way. Any preparation ended in 998.M41 when five Shrouds launched a suicidal assault on the Adeptus Mechanicus' Mars instillation.
It is unknown why the Necrons performed such an apparently pointless mission. The Adeptus Mechanicus have been reluctant to discuss the incident, although they have placed a perdita zone around Noctis Labyrinthus enforced by an entire Skitari Legion.
Since the Mars gambit, Shrouds have been identified on six occasions acting as the long-range eyes and ears of the Necron fleet. They excel at their job because no Imperial ship with any chance of catching a Shroud could possibly defeat one if they caught it. They pose a grave threat to Imperial Navy installations. If they can penetrate the defenses of Mars with such ease then there is no base which can be considered safe.
