Originally Posted by Tavar
This was fighting on a Tomb World, was it not? And one where the Orks had some control over the upper levels? Sounds like a massive host for the orks, and time for the Necrons to pull out all the stops.
The Necrons were also of the insane variety and the Culture planted themselves right in the middle of the conflict (right on top of the entrance to the Tombs).
That was when the Necrons attacked with the monoliths. This was towards the end of part 6's chronology if I remember correctly.