The Necrocrafts are the ships used by Nebula and the Sakaarans under the orders of Ronan the Accuser.
Korath the Pursuer used a Necrocraft to travel to Morag to obtain the Orb.
After the Guardians of the Galaxy escaped from the Kyln, Ronan the Accuser ordered Necrocraft sent to all corners of the quadrant to find the Orb.
During the Skirmish on Knowhere, Nebula and Sakaarans used Necrocrafts to chase Gamora.
During the Battle of Xandar, the Sakaarans used the Necrocrafts to dive bomb Xandar.