A Doomsday Monolith is found at the centre of a Doomsday Phalanx, and is a heavily modified Necron Monolith protected by an unknown design of energy field. It is capable of focusing awesome destructive energies, and is more powerful than a regular Monolith.
A Doomsday Monolith possesses a power matrix nearly identical to that of a normal Monolith, with one difference. Instead of firing a Particle Whip, or translocating a Necron unit, the power matrix energy can be discharged in the form of a Gauss Obliterator, a stronger form of the Particle Whip which affects a larger area.
Phase Shift Generator
A Doomsday Monolith is equipped with a Phase Shift Generator, which functions differently to the Phase Shift Generator on the Gauss Pylon. It affords the Doomsday Monolith additional protection, increasing its survivability (though not that of other nearby Necrons).
Instead of firing a particle whip, or teleporting a unit, nearby Monoliths can grant the energy from their Power Matrix to the Doomsday Monolith, which is capable of focusing this power to increase the intensity of its Gauss Obliterator.