I've noticed that there's been a increase in popularity of muta play in PvZ recently, and not surprisingly, an increase in the number of [H] PvZ muta threads as well. Instead of replying to each of those threads with the same things, I decided to just start this topic and share my thoughts here on how best to play against mutas in PvZ.
Also, this discussion is more oriented towards playing out the long macro game against mutas. Going 2 base all-in and trying to kill the zerg before he gets mutas or right after he gets mutas is certainly a viable option, but I’m not really going talk about that in this thread. The reason is that either the 2 base all-in is pre-mediated (so you were planning to all-in regardless of the zerg going mutas or not), or you weren't planning to 2 base all-in but upon scouting the spire you decided to attack, and in that case you either succeed and win or fail and lose. Either way there's not much to discuss.
Two things I want to mention here. First, obviously you want blink stalkers to fight against mutas. Throwing up stargates for phoenix after you scout mutas is not a good response (more on that later). It doesn't actually matter what build you already started doing, but as soon as you scout the mutas, you need to change your build accordingly. If you went robo and planned to go colossus and already have a robo bay, that's fine. Just don't make/cancel colossus, add a twilight, and research blink asap. If you went stargate, it's fine to continue making phoenix to help counter mutas, but you still want blink regardless so get that council asap. Basically, whatever build you started with, as soon as you see spire/mutas your immediate goal is to have at least blink with 6-8 gateways off of 2 bases.
Second, and this goes beyond anti-muta play, but builds that blindly mass sentries at the beginning are bad. Getting to 8-12 sentries early game seems to very common in PvZ but IMO it's just not a good idea unless you are committed to doing an early 2 base all-in. I know that guardian shield is great against the bounce attack of mutas, but what's going to end up happening is that your sentries are going to get sniped and it'll just be a huge waste of gas that could have gone to additional stalkers and HT. Sentries are also a huge waste against infestor/ling play, baneling play (with drops), and any more than a moderate amount (like 4-6) will be a waste against early 2 base hydra play. Basically I only start with 2-4 sentries (note this is off a FFE, so if you're gate expanding you could use a few more), and only if I scout roaches do I add more sentries.
2. Unit composition
You want blink stalker + zealot + HT to fight against muta/ling. I personally like to keep about 3-4 HTs with my army, while leaving 1 HT in each of my bases as well. As the game progresses and more mutas come into play then you can increase the HT count, but the rest of your gas should be spent on stalkers. No pre-emptive archons (make archons after you storm, but don’t pre-make any archons). It may be tempting once you have some HT already to make some archons as well, but you will always be better off with more HT and/or stalkers instead. You can add in a couple sentries if you want but I don’t bother since they are easily sniped. The zealots are really important not just as a mineral dump but to fight against lings. You never want to move out with pure stalkers because that will get overrun by lings. Also with enough zealots then you won’t need to use precious storm on lings and can save them all for muta.
As for phoenix, although they are great against mutas in low numbers, trying to transition into phoenix if you don’t already have a stargate is too late since you will never be able to match his production. By the time you get out a decent number of phoenix he will have 20+ muta and while theoretically you can kite him forever every slight mismicro you commit will result in you losing a phoenix or 2. If you already have a stargate though from a stargate opener then it’s ok to make some phoenix to help deal with the initial harass. I would still eventually stop making phoenix if he commits to mass muta though. If you’ve opened dual stargate and he goes muta... well that should be an auto win for you (unless you blindly go mass voids and don’t scout the muta. In that case you should switch to phoenix).
3. Establishing your 3rd
This is a common frustration I've heard - I can't seem to secure my 3rd base with mutas and lings harassing everywhere! The seemingly contradictory answer to this is to try to set up that 3rd earlier. The later you try to expand to your 3rd, the bigger the muta ball is, and the harder it will be for you to safely get your 3rd up. When there’s only 12 mutas in the muta ball, it takes awhile for the mutas to actually kill a nexus warping in, and thus you have some time to get your stalkers there to defend. But when the muta ball gets to 20 or 30 mutas, they can do an insane amount of damage in the seconds it may take your stalkers to get into position to defend.
By the time you’ve scouted the zerg going mutas, if you’re not going to 2 base all-in the zerg, and you’ve started blink research (yes that’s right you can and should start trying to expand even before blink finishes), have a few cannons in your mineral lines, and have some stalkers out to chase away mutas, you need to start trying to take your own 3rd. Notice that I say “start trying” to expand, meaning that it’s ok if you start the nexus and pylon but then mutas and/or lings come and force a cancel. It’s basically just a low risk/high reward tactic, if he forces a cancel you only lose some minerals and that’s no big deal since it’s your gas that’s what’s really valuable.
Another thing to remember about battling muta/ling is that muta/ling is weak in a straight up fight. Against standard roach play if you try to expand to your 3rd too early then the zerg can just attack and kill you, but when the zerg goes mutas his army isn’t actually that strong and he can’t just attack and kill you.
4. HT vs archon
After you get some blink stalkers out on the field, and as the muta flock grows bigger, you need a templar archives to continue battling mutas. Lots of people say archons are great against muta/ling, but I completely disagree. Archons suck against mutas. They also suck against zerglings. Ok fine, they don’t actually suck, I’m just comparing them to archons vs mutas and lings from BW :p But the reason why I don’t like archons against muta/ling is not because they’re bad, it’s because storm is so much better, in every situation. Archon splash is just pitiful and can be combated via magic box, also their cooldown is not that great so when the muta flock gets really big archons can be picked off while getting in only 2-3 shots. Meanwhile storm has a much larger radius, a much larger range (9 vs 3, especially important when defending against harass) and storm keeps working even after the HT dies (and the HT will die, mutas will of course pick them off but hopefully not before you get off the storm and deal 20-60 damage to a big portion of the flock). Also against zerglings, you have zealots to counter those. You shouldn’t be relying on stalker/ht/archon to fight against zerglings.
There are 3 situations when you want to make archons. 1) After you’ve stormed. Mutas usually target HT as their first priority so it’s rare for a HT to live long enough to gather energy for another storm. 2) You have 2 or more HT near each other, mutas have spotted them, but you don’t have energy to storm. Spam that c key lol. 3) For some reason you have a ton of gas and not a lot of minerals. If you have a ton of gas AND minerals then your macro sucks and you should just make more stalkers. But it’s not uncommon for the mutas to have done enough economic damage that you end up starved for minerals but with a lot of banked gas. In that case having like 10 HT in your army for storm is overkill and it’s ok to make some archons.
5. Defending multiple bases against harass
This is probably my best piece of advice in this entire thread. Observers. Make 4-5+ of them. I know they cost quite a bit of gas, but it’s well worth it. Also you won’t be using your robo for immortals or colossus anyway so that’s not an issue (which normally is a huge issue against other builds). Spread the observers around the map so that you can detect where the muta ball is at all times and then you’ll have a lot of advance warning where the mutas will strike next, giving you time to move your stalkers in position to defend. It can also be helpful to split your stalkers into 2 separate groups and keep them in separate bases. However if you get your observer network set up then this isn’t even really necessary.
You’ll need a few cannons in each mineral line early on, which will mainly serve to buy you time for your stalkers to get there. I usually get 2 cannons per mineral line, but anywhere from 1-3 should be fine. As the muta ball gets bigger you will need to leave a HT in each mining base, and stop relying on cannons. You can add more cannons as the muta ball increases in size, but I don’t find that it’s worth it and I’d rather spend extra minerals on more zealots. Speaking of extra cannons and zealots, it is a good idea to have extra cannons and to leave some zealots in your 3rd, since a really common maneuver for the zerg is to send mutas into your main while streaming in lings into your 3rd.
Note: while I personally prefer having more zealots and less cannons to defend each base, it's not a bad idea (and safer too) to mineral dump on more cannons instead of zealots as the game goes on. Having 6 or more cannons in each base late game can help to buy you even more time against bigger muta balls.
6. Harassing and attacking
The strength of muta play is the ability for the zerg to expand everywhere and keep the protoss in his base. Most of the time you’ll have to rely on harass via DTs and/or zealots to try to kill expansions since if you move out with your main army mutas will just counter into your base as soon as you leave. DTs are a bit of a gamble since they cost a lot of gas but can be really effective at taking out expansions. If you use zealots, I highly suggest harassing with them only when there’s a battle going on or mutas are in your base. Also, avoid watchtowers or use a warp prism. The zerg will generally have map control and there’s no point in trying to harass with zealots with mutas flying around in the middle of the map picking them off.
As for actually moving out (which you’ll have to do eventually), in most cases you shouldn’t move out until you are maxed. Until then, don't panic and stay calm, don't feel the need to move out prematurely. It's ok if the zerg takes the entire map and a billion expansions, he can't kill you. So when should you finally attack? When you army is big enough so that you can attack with the majority of your army while still leaving some at home to defend the counter. Usually this is when you're maxed. The important piece is having a lot of HTs, spread out amongst both your army and all your bases. If you had great success defending against muta harass (little to no damage done, you took your 3rd decently early, and you’ve killed some mutas), then sometimes you can move out before you’re maxed. Just make sure that you have enough HTs both in your main army as well as back at home when you do so. Storm is the key.
7. Zerg transitions
There’s not much to say here, except for the fact that you should pay attention to possible zerg transitions and not let them catch you off guard. This generally means having an observer either at his rally point or in his main base to check his tech. The most common transition is to roach, in which case you should add immortals into your army. Blink stalker/zealot/HT is already a fairly versatile composition, and you don’t really need to change your composition if he adds/transitions banelings, infestors, and/or hydras. As for hive tech transitions, ultras can be extremely dangerous if you don’t scout them in time. Obviously if you scout ultra then you need to add immortals. Against brood lords, there’s really nothing special you have to do since brood lord/muta don’t synergize well and mutas are terribly supply inefficient in a straight up fight.
As for your own tech, if you get to 4-5+ bases, I highly recommend teching to mothership. Both vortex and mass recall are insanely useful for obvious reasons against muta.
8. Other tips
Upgrades are extremely important, including armor. Make sure to get both attack and armor upgrades against muta/ling. Although I’ve only used 1 forge, going dual forge may not be a bad idea.
Keep expanding! There’s no reason to be satisfied with 3 bases. When your 3rd base is secure, start looking to expand to your 4th. Then your 5th. Don’t stop expanding, expanding doesn’t cost gas.
When engaging mutas with blink stalkers, don’t blink into them. Walk up to them, and then you’ll be able to blink to chase as they run away.
Keep important tech buildings away from the edges of your base. Watch out for artosis pylons. There’s no need to put pylons around the edges of your base against mutas.
Never base race against mutas. Sometimes the mutas may get into a mineral line and cause some damage, and you may be tempted to just say screw it and go all-in, but resist the urge. Stay calm and focus on defending.
Cannon placement: keep cannons close to each other so that mutas cannot pick them off 1 at a time. Also, build them on the side of your minerals that face the direction mutas will likely come from. For example, if you are at 9 o'clock on shattered and the zerg is at 6, you should place the cannons near the bottom of the mineral patches. (thanks monk!)
As you're getting close to being maxed, it's a good idea to add some immortals into your army even if you didn't scout roach or ultra transitions. Immortals are extremely helpful against the inevitable spine crawler walls you'll have to break down. (thanks aa.spoon!)
A note on storming: make sure you're targeting underneath the mutas (their shadow). Turn flyer helper on in settings.
The most important things when fighting muta in PvZ:
Mass blink stalker + zealot +HT. Phoenix and archons are bad.
Put observers around the map to track muta movements.
Expand early and often.
I was planning on uploading more replays, but I decided to go for quality instead of quantity. Here are 6 recent replays from ladder, practice, and tournament games. First 2 replays are the best ^^