Story prediction right here. The ghost needs to activate some device/computer/door. Waves of enemies come. Occasionally a captain/minotuar/witch/centurion or 2 arrive. Dispatch. Move to next device/computer/door. Possibly named mob that is one of the already base models of enemies, usually the same attacks but some might be the same exact but much larger with the weaknesses in the same exact spot. Pump full of lead/energy/explosions. 30 seconds til orbit. Repeat.