Cults of Destruction; Destroyers
So necrons for 7e have been here for a while, and I have yet to see any comprehensive tactica on these guys yet that can account for a variety of situations on the tabletop battlefield. I will attempt to rectify this in time, and for the time being I will start with a unit most long time necron players will know and love; the Destroyer.
Waaay back when, the destroyer was a go to necron unit because of its high strength gun, long range, good rate of fire and its speed. Plus being a necron, he was resilient to boot. The 5e codex saw these guys somewhat overshadowed by changes to their rules and others, tomb blades became a cheaper and faster alternative due to him being changed to jump infantry instead of his old jetbike form, and the added buffs to wraiths and scarabs made the limited fast attack slots harder to justify for our death obsessed friends here. Little has really changed in that regard, scarabs and wraiths remain lethal at close quarters, and the destroyer still carries his altered rules from the last codex, but there is one thing we can quite clearly take advantage of.
The Destroyer Cult formation. Why? Well let's take a look. The Destroyer now packs a gun that fires two shots, has a strength of five and an ap of three. That's dead space marines on a 3+ and who doesn't love that? But it gets better. The cult formation gives us rerolls to wound and armour penetration in the shooting phase, coupled with their preferred enemy special rule making these guys efficient killers. Then of course there are the benefits of gauss weaponry against vehicles, and you can add versatility to a destroyer heavy list as well.
The change of unit type to jet pack infantry is also worth a look, as it gives them additional movement during your assault phase (just like dirty dirty tau) and grants them the ever pleasant option of deep striking onto the battlefield. And of course, it makes them relentless allowing them to lay down death while on the move.
So how does this work for you? Well, a destroyer cult formation requires a minimum of three units of destroyers which are three models strong each, as well as a destroyer lord and option for a single heavy destroyer unit as well. This can count as a detachment in itself, and if chosen as your primary grants your destroyer lord a reroll on the warlord table if you use the necron codex traits. This amounts to about 470 pts at its most basic, so lets allow roughly 500 or so assuming the lord will take a toy or two. Conservatively, you could take three such cults as a single 1,500 pt army and be the bane of most marine or marine equivalent armies out there. Your destroyers will have maneuverability and range to deal with almost any army, however you will be sorely outnumbered and are only likely to enjoy a fair game against small elite marine armies like grey knights. Great for theme and fluff, but I'd recommend against it for casual gaming.
Far better that you take this formation as a complement to a more traditional firebase oriented list. Using the standard Force Org chart from the big rule book, You can build a footslogger based army of immortals or warriors backed by a cryptek or lord, or maybe even something heavier like a monolith or c'tan shard. This leaves you with the option of choosing them or your cult as your primary detachment depending on your preference, and remaining points after building both cores can easily be plugged by adding more destroyers or more warriors/immortals. Using the standard force org also allows you to take a unit of triarch praetorians, which make a much better deep strike escort for your Destroyer lord than his own destroyer kin. Drop them in together, then in the following turn they can go their separate ways allowing the normal gun toting destroyers to deploy well clear of the swinging blades.
Additionally, this method also fits quite comfortably with the decurion detachment setout, allowing that same traditional army list. However the minimum requirements of the reclamation legion may make points tight if you play a smaller game.
Remember, a lot of people will instinctively gravitate towards building a decurion army list simply for the benefit of that bonus to reanimation. There is nothing wrong with this of course, in fact it's quite advantageous to do so, however be wary of taking it for that benefit alone when maximizing other strengths might serve you better. All formations have benefits and drawbacks, and following a template for one reason (no matter how good) can often blind you to other opportunities when building your list.
Nonsense is our Salvation