Previously, I mentioned I was looking at Codex: Necrons as a core army to field my Mechanicum. Here’s my pondering.
Before I look into the Codex, I looked at potential allies to see what other options are available:
Necrons are convenient allies with Chaos Space Marines, Tau, Grey Knights. They’re desperate with other Imperial forces. I will simply ignore desperate allies, as I’d rather the army work together in at least some co-operation. Convenient allies don’t get any negatives (but also get no benefits!).