Ok so let’s analyse the most common reasons for having allies in your army. In 6th ed there seems to be a number of reason you would like to take allies but I think 3 reasons at high level tournament play you would need allies, these are.
++ No way to kill Flyers
+++ Crap holding units
If your army has these problems it probably needs allies. So do Necrons have these problems?
+ So do Necrons have flyer options and are they good? The night scythe is a fantastic transport (also is the only flyer available as a troop dedicated transport), is cheap has a big gun and the new FAQ makes it even better. The Doom scythe is the second flyer option open to them and it is pretty awesome too as it has one of the best guns in the game. Kaelarr had done a list of flyers and how good they are. This is covering all flyers so you can decide if your army needs a flyer allies. The link to the post is here. So the answer to question 1 is YES.
++ Do Necrons have a way to combat flyers? Having their own flyers is a massive plus point here but they also have the dreaded twin linked tesla destructor a monstrous weapon that averages 3 hits a turn on flyers at s7 without skyfire scary stuff. So I think it’s safe to say Necrons are 2 for 2 on this so far.
+++ Do Necrons have good troops? Necron warriors are space marines with a 4+ save, but can also get up on a 5+ from anything, bring a gun to the table that can damage anything in the game a boast an amazing leadership 10, Immortals bring all of that but with an improved save 3+ and access to bigger and better guns both bring the option of a flyer transport. Hmmm I’m gona go with a YES for this.
So to summarise Do Necrons need allies? NO, Can allies make using Necrons more fun? YES. Do they throw up new weird and wacky conversion ideas? YES. Do they help bring beardy combos to a gaming table near you? YES. So do Necrons need allies I would say YES just ask those poor Nid players. Clear as mud!
Next post I will put up which allies would help Necrons if like me you like the idea of adding in some other toys to your collection.