Megalith
Megalith are Monolith and Doomsday Monolith's father and is thus, very large and very powerful. Megaliths are enormous mobile fortresses, in fact they are so large they can carry multiple Monoliths within its hull, releasing them like a swarm upon the battlefield like a giant Necron Matryoshka Dolls so you can shoot Gauss cannons while you shoot Gauss cannons.
Other than its humongous (humongous what?!)(size and capability of shoving as much Monoliths as possible. The Megalith is also equipped with an arsenal of devastating gauss and particle weaponry far more powerful than your standard issue Monolith. The Megalith is fully capable of space travel as well as planetary landings, and is used to initiate full-scale planetary assaults against hardened targets, usually from planetary orbit.