We’ll be looking at this set from the perspective of player 2.
There’s a lot going on in this set. For absorb, there’s Doomed Wall. Typically you’d expect a medium or medium-high economy (aka, somewhere between 14 to 20 Drones) with Doomed Wall as your absorber, depending on how aggressive the rest of the set is.
The rest of the set is definitely aggressive. There’s two aggressive legendary units in the set – Tia Thurnax and Vai Mauronax.
Tia Thurnax by itself isn’t much of a threat to a high economy strategy – it’s killer against someone who can’t make a lot of defense in a turn (e.g. when they’ve committed to Red), but is ineffectual against someone with a big economy and a defensive tech setup. Vai Mauronax, on the other hand, can easily outvalue any high economy doomed wall centred strategy, as long as you could get it out. And, looking at the rest of the set, getting it out would be a piece of cake against a high economy strategy. You’ve got Blood Phage, Ossified Drone, and Ferritin Sac, which are all great support units for a big red unit – they let you sink your Red and get out defense, which shores up the two primary weaknesses of a big red strategy.
The support for Vai is so strong that at this point it’s my clear front-runner strategy. If you can get Vai up without dying, you should easily beat any non-Vai strategy – not only will you have your powerful attacker out, but you will be able to absorb on Doomed Wall while your opponent won’t have that option (since if they went for it, Vai could freeze it until it died). The obvious start for a Vai strategy would be natural Animus for player 1, or Fastimus for player 2.
Now that we’ve identified a front runner strategy, we can consider if there’s any counter strategy that beats it. If there isn’t, then we can safely assume both players are going for Vai and think about what the best way to win the mirror is. The obvious counter strategy is some kind of Tia Thurnax all-in. As I said earlier, Tia Thurnax is bad against defensive high economy builds, but is excellent against aggressive, heavy red strategies that are weak on defense, like Vai. So, if our opponent goes natural animus with a view towards getting Vai out, how would we try to beat that with a Tia strategy? To me, the build that leaps out for player 2 is 1. DD 2. DDC 3. DA 4. R5:
This will let us get Tia next turn. If our opponent continues to commit to Vai, by getting a second Animus, we could easily kill them with a Tia. However, by making the Conduit and floating two green, we’ve tipped our hand that we’re going for Tia. So, our opponent can shift from aiming for Vai to a more standard blue-red strategy that should (with the help of Blood Phage, Doomed Wall, and Ossified Drone) be able to hold a Tia all-in. We could try to delay our Tia Thurnax, but it’s going to be difficult to win a longer game when we have a Conduit that can only be used for Gauss Charges or the occasional Borehole Patroller. Every turn we delayed Tia we’d be falling behind more and more in the value game. Because of this, I think that Tia probably can’t beat a Vai strategy.
So, I think we can assume that the game will be a Vai mirror. As I mentioned earlier, the best way for player 2 to do a Vai opening is to open with Fastimus. This is because you want to get your Vai support units – especially Blood Phage – out as soon as possible. If you delay your support units until after Vai, you will find yourself unable to spend your four Red the next turn – on the other hand, if you have e.g. bought a Blood Phage and an Ossified Drone prior to making Vai, you can click both of them after your Vai to efficiently sink two of your Red.
Once you’ve gone for Fastimus, assuming your opponent responds with Natural Animus, you have two main options: you can go Blood Phage plus Ferritin, in order to buy an Animus next turn and get Vai out the turn afterwards, or you can go Blood Phage plus Ossified Drone, which will take a turn longer to get Vai out but should be a bit more safe and solid.
Option 1 looks something like this:
Option 2 looks something like this:
There’s a ton of different ways to execute your Vai build in this set, and it’s still possible that a Tia based strategy could work. That said, I’d go for the Fastimus into the faster Vai.