The point of this guide is to show you how to exploit the fact that unlike siege tanks, the thor’s splash radius is EXTREMELY small, and only really takes effect when mutas start to overlap and stack.
The SC2 Magic Box
In BW you could use magic boxes for spell spread, among other things. In sc2 we have smart casting so that isn’t important, the application this time will be to maintain a unit spread. The magic box is basically an invisible box that fits around your selected units. If you right click inside the box, your units will try to bunch up at that location. And if you right click outside the box, they will maintain formation and hence retain unit spread.
(it’s actually more of a square but from that angle I had to make it a rectangle.)
What's better is that the unit spread is automatic. You know when you bunch up a group of mutas and they start to diverge on their own? Once they reach THAT spread, THAT is your anti-splash damage formation. The thor’s splash damage is literally that small. See that picture up there? That is all the spread you need to completely eliminate splash damage. And you don’t need insane micro skills to maintain it. Just bunch them up once, wait until they diverge, and move them out, being sure to always click outside the box.
There is more to magic boxes though. In particular they have a maximum size depending on whether air or ground units are selected. If the selected units exceed the maximum size of the box, they will always lose formation no matter where you click. Fortunately the air box is MUCH bigger than the ground box. Mess around with about 4 zerglings and see how much you can spread them and move them while keeping formation. They don’t spread a whole lot. Air units are very different. I have found that I can keep a formation of 36 mutas without them getting outside the box. If you go above that number you’re risking one of them getting outside the box, and the result will be all of them bunching up during a move. It’s safest to keep your numbers lower than 36. So just keep an eye on that.
WHAT NOT TO DO
DO NOT. I REPEAT DO NOT, attack thors by simply right clicking them from a distance, or this is what you will see. I shake my head in shame whenever I see this. (Although as a terran player it does make me a happy camper).
WHAT TO DO
The idea is to move, park, and fire. Let’s say I want to pick off 2 thors with 10 mutas. First I get them in formation. To do this bunch them up and let them diverge into a nice little circular cloud (you should only have to do this once before moving out). Second, once you see the thor, FORCE MOVE to a point past the target thor. Once your mutas have clouded over the thor, attack the target thor, and ideally you will see your mutas get this nice momentum where they do an attack before they come to a complete stop, it’s very important that your mutas are all in range before you attack. Otherwise they could bunch up slightly. As you focus one thor down, watch to see if another thor is accumulating glaive damage. Kill that one next. If he is very close to the other thor you may not even need to force move your mutas. Additionally, you may find it difficult to click on the thor when your mutas are surrounding it. This is actually a very important issue, because if you click on one of your mutas or the ground right next to him on accident, the results will be disastrous. The solution I have found is to just hit “end” on the keyboard or use your mouse scroll to get a better angle. I know it’s awkward and not very pro but it’s much safer. You will find that it gets harder to do this with no bunching as your numbers get bigger. A bit of practice on a unit tester couldn’t hurt you there.
These are by no means proven, but I have found that at about 18 mutas, you’ve reached a critical mass where mutas are even with thors at a 3:1 ratio. So 18 mutas is about even with 6 thors. Do the math: 300/300/6 is even with 300/200/6, even when the latter is supposed to be a counter and the sole AA in a mech army I might add. As you get lower in mutas, the ratio gets bigger. As you get higher, the ratio gets a little smaller. Using this tactic, 4 mutas is basically even with one thor. This does not take into account upgrades but I will discuss them further down. Again I want to stress these are by no means proven. Results have varied tremendously before. Perhaps the mutas bunched sometimes and I missed it. Perhaps the thors were doing an absurd amount of overkill, causing their DPS to plummet. No less, the technique makes a gigantic difference in the LIFESPAN of your mutas while they’re around thors. This enables them to harass more effectively when the terran is using thors as his primary air defence, and much more.
Now some important figures: with no upgrades on either end, thors kill mutas in 3 hits. Thors with level 1 weapons and mutas with zero armor still kill mutas in three hits. With level 2 weapons, thors kill mutas in two hits unless the mutas have level 1 armor, then it takes 3 again (In this case mutas will have ONE HP left after the second hit due to that instant point of health regen).
What can the terran do? Certainly armor for thors will help as the glaives hit multiple times. But a better tactic is just spacing out the thors and taking advantage of their range. This will increase the time it takes for the mutas to get from one to the other, and eliminate glaive damage to an extent. Also, make good use of your SCVs.
What can the zerg do extra? Possibly get corrupters and use corruption to help the thors go down faster. Don’t necessarily target the thors. If you can pick off his tanks, you can pave the way for your ground army to mop the floor with everything else, which leads to the next point. Obviously don’t make ALL mutas unless you can see he’s really short on thors or AA in general.