A Sepulchre is only utilised by the largest Necron vessel in a given fleet. When a Sepulchre is used to attack an enemy ship that has foolishly come within its range, a wave of palpable psychic force is generated and sent outwards in all directions.
The enemy’s crew are then paralysed by visions of horror, and if discipline is lost, then the crazed crew are likely to do damage to their own ship as they rampage uncontrollably through its confines.
- Battlefleet Gothic Armada Rulebook (Specialty Game), pg. 73