Obelisk
Obelisks are enormous Necron war machines and are much larger than your standard Monolith. These engines of war specializes in air defense. They are able to remain dormant beneath Tomb Worlds for millions of years, when awakened by their Necron creators the Obelisk rises from the earth and levels out far above the surface, blasting enemy aircraft out of the sky and melting infantry with its unholy amount of Dakka from its Tesla Spheres. For exceptionally larger flyers like a Manta for example, the Obelisk would then use its Gravity Pulse, which is a weapon capable of creating an expanding sphere of earth-shaking gravimetric force that rips apart the giant aircraft out of the sky and turns your $1000+ model into the trash can.
The Living Metal walls of the obelisk are lined with Canoptek Leeches, allowing it to self-repair in battle. Coupled with the fact that Necrodermis is already tough beyond proper reasoning and able to regenerate on itself. This makes the Obelisk not only an annoyance but a really tough to kill annoyance.