So about those Necrons

[Kilofix]

Going to keep this within B&C rules and only refer to Necrons in the context of minor Allies to CSM.

 

That said, I wonder if the Shield of Baal: Extermination book will have any small Necron Formations that would be worth pairing with Chaos Space Marines.

 

Something like a Formation with just a couple of Spyders and some Scarab groups could go well with screening in front of Maulerfiends, etc. Might even be able to paint them up in Word Bearer Daemon Engine red.

 

Since Necrons are AoC with CSM and we won't run into OEO.

[Lord Asvaldir]

Hard to say if the new formations will be useful until the rules are out. 

[Scribe]

Conceptually though, a solid bit of shooting from a Necron formation would not be a bad thing to add.

[ThatOneMarshal]

You could even use them as evil chaos androids like the ones from the early days of 40k.

[*Furyou Miko]

If there's anything usable, it'll be towards the higher-end Necron units - mindless Canopteks aren't likely to be updated to use the new routines required by a formation for use by friendlies.