When Building lists, I love to theme them to particular styles of play or even pure thematics. My favorite happens to be a Maccragge vs Behemoth them (what I am working to convert my army to). But this goes beyond cosmetics. Building a themed list can be a great fun and usually quite a challenge. For those who are used to playing with steamrolling, power-playing lists, this is not for you. Many of the themes we can use are not highly competitive or at least take more skill to use than going with the "meta" lists. So as you continue to read, be warned that these are more for fun than effectiveness, but do not underestimate them.
Our first Theme is based on a hive fleets first encounter on a planet. This theme is about guerrilla warfar and ambush tactics. With the addition of the Vanguard Dataslate, we can field a separate detachment of Lictors or Genestealers that adds a bit of flavor and fun. Aside from these (which I will talk about in a different post) here is an example of a vanguard list. This list is perfect for a Leviathan paint scheme.
Deathleaper
3x Lictors
3x Lictors
3x Zoanthropes
15x Genestealers + Broodlord/acid blood
15x Genestealers + Broodlord/acid blood
30x Termagaunts
30x Termagaunts
3x Warriors/rending claws , 1x Deathspitter (5 point dump)
=1500
This is centered around using the genestealers and the lictors to harass and pin down the opposition. The weakness of this kind of them is lack of dedicated anti vehicle/heavy infantry. That is the only reason the Zoanthropes have been included in the list (and synapse). The second issue is synapse. While lictors have high leaderships and genestealers do not need synapse, the rest of the army does and a group of fearless genestealers is kinda scary. Another option which is a bit more gutsy is to take horamagaunts instead of termagaunts. this means they are less likely to be useless failing synapse, but they could just kill themselves instead. This is a fun list type, but very difficult to use, especially against marines who can outlast you.
The second list that comes to mind is the flying list. It is rather easy to make one. Use flying tyrants, harpies, gargoyles, shrikes, and if you really want to, flying rippers. The troops are harder to make fly, but a few units of gaunts isn't that hard to adapt to especially if you use hormagaunts who can actually keep up with your flyers. This list is all about hitting fast and hard. Its a high risk high reward strategy that tends to die more often then win. But there are few things more frightening than seeing an entire brood of gargoyles and shrikes coming straight at your face. The issue here is it does play well to objectives without some serious strategy. It likes to engage the enemy and kill them, which is still a viable option. also if you want large broods of flyers it is gonna cost you some points/money. Fun but difficult list.
The next theme is a subterranean assault. I know a guy who runs a variant of this and it is nasty when used right. You max out all trygon primes and bring 3 broods of raveners. bring a brood or two of lictors to prevent scatter and tada! nasty deepstriking mayhem (you could also add a flying tyrant for deepstrike). Bring some gaunts in the rear (maybe a tervigon troop) and you can do some heavy damage with a wave assault. Also bring a comm relay for reserves since you cant get the upgrade on a standard tyrant anymore. The ONLY way for this list to be viable is three trygon primes for synapse. Any other way to run it has been unsuccessful from everything I have seen. If you love the idea of dropping three MCs on your enemy and smaller yet no less nasty worms, then this list is for you!
The next two lists are not too uncommon (actually they are the most common). Swarm and Nidzilla. Nidzilla is bringing MCs and as many multi-wound or high toughness things as possible. Runs the risk of getting shot to bits by heavy weapons, but so cool to see so many big bugs moving forward. Swarm is bringing the tervigon (maybe 2-3) and using warriors for synapse. You rush tons of little guys at your enemy while supporting with specialized elites (zoanthropes) who do what your gaunts cannot. Also a wonderful list to see fully painted and on the tabletop.
I didn't give lists for most of these due to how easy it is to see a functioning list. I see the vanguard theme as the most difficult to use due to its fragility. Now these aren't the only ones you can make. Try creating a digestion theme using organisms involved in the final stages of the planetary digestion or perhaps pick a hive fleet and try to theme around their recorded strategies (lictors being very common in leviathan). If you think of any others post them and I may try them out! hope you enjoyed this section of my Tyranid Tactica!