This guide doesn't seek to give earth-shattering advice that will shock your world. It simply looks to be a one stop collection of advice on Mutalisk control. It's going to be wordy. I'm going to use more paragraphs than I should simply to make it easier to read.
Early-game Mutalisks are harassment units and should be used as such. They should never directly engage an army. Their strength lies in their mobility, picking off stray units, workers and buildings. Because no unit is fast enough to keep up with Mutalisks, they provide indirect map control - if your opponent splits his army to attack you too early, Mutalisks can deal quite a headache by targeting undefended areas of your opponent's base and retreating once the defending army arrives.
The number of Mutalisks you decide to make is critical, specifically against Terran. For example, against Terran you will need 5 Mutalisks to kill a Turret in 5 group shots. 6 Mutalisks can kill the same Turret in 4 shots. 8 Mutalisks kill a Turret in 3 shots. It takes 12 Mutalisks to be able to kill the Turret in 2 shots. You can see that you are getting diminishing returns as you are adding Mutalisks to your group. So where is the ideal point to stop? It is ideas like this that this guide will try to give tangible rules and suggestions, while keep in mind that not every game can follow the same pattern.
Let's get this out of the way. In order to make your Mutalisks clump up and look like a single Mutalisk, simply group them with a unit that is far away. There are two viable options, a Larva or an Overlord.
The advantage of the Larva is that it is unable to move, meaning you will not have to worry about where it is when controlling your Mutalisks. A big draw back to using the Larva is once it is morphed into an egg, it is removed from your group. If you aren't quick to notice, your Mutalisks will become unstacked and become much harder to control.
The Overlord is the better choice. Although there is the possibility of the Overlord flying into harm's way, losing an Overlord is much better than losing Mutalisks because they were unstacked and you couldn't control them. Ideally, if you notice your Overlord nearing the enemy base, stop it and remove it from the group, and then add a new Overlord from your base to the group. One note is not to add an Overlord you were purposely leaving behind for detection to your Mutalisk group.
Now that your Mutalisks are clumped up as one, you want to make them fire at the same target. This is particularly true against Marines and workers - you want dead units. Dealing a bit of damage to all units does you no good.
Mutalisks have quite a range. Unfortunately, their AI is dumb so you rarely see it. If you attack-move a Mutalisk and let it acquire its own target, it will not find the target until it is in range, and then it will begin to decelerate and fire. This is why Mutalisks often look to have a small firing range, while human-controlled Mutalisks seem to have double or triple the range. To avoid this problem you have to control your Mutalisks. Always give them a target, never leave them on stop, attack or hold position.
To add to this, fight_or_flight asks "I have a question....sometimes I just tell the mutas to hold behind a mineral line that is hard to defend, but they end up just sitting there, not attacking. Is it because they have been hit by a unit that is out of range? Any solutions?"
Yes, if there are enemy fighting units around, your Mutalisks will not attack any non-fighting units or buildings until those fighting units are out of range or dead. This is why giving Mutalisks targets is so important.
Never let your Mutalisks decelerate, as their relatively slow acceleration could mean big problems when an army comes near. This is why you will often see progamers dancing their Mutalisks at full speed when there is no harm in sight - in the event that an army is arriving, the Mutalisks will already be at top speed and can easily escape. You should practise keeping your Mutalisks mobile and giving them targets.
In this vein, Mutalisks can only shoot in the direction they are facing. If you tell a Mutalisk to attack-move behind it, it will decelerate, turn around, and fire - an unfavourable result. Mutalisks can, however, turn around without decelerating, meaning if you first tell the Mutalisk to turn around, and then give the attack command (or much easier, simply target a unit behind it), it will happen much quicker. Once you've mastered this, you can issue a turn around command, then the attack command (or target a unit behind your group), followed by another turn around command, which will result in your Mutalisk essentially flying at full speed while firing backwards!
Now that you have a feel for the above points, you need a feel for Mutalisks cooldown. Cooldown is the time a unit must wait after attacking to attack again. There's no way I can explain Mutalisks' cooldown length to you in a meaningful way. If I were to guess, I'd say it's about 0.7 seconds. Does that help? Of course not.
The last decision to make regarding Mutalisk targeting is whether you should you attack with a right click or an attack-move. With all other units it's much more beneficial to use attack-move, because when you misclick, your units will still attack. When you misclick with a right click, your units simply run into the enemy. Because you should always be watching your Mutalisks, misclicking shouldn't result in many problems. Essentially, use whichever attack method you are more comfortable with.
Now that you have a feel for their range, speed and cooldown, you can start practising "sniping" units with Mutalisks. The methodology is simple - fly grouped Mutalisks straight at their target. Some time before they are in range, issue the command to attack. As soon as you fire, retreat your Mutalisks back a ways and then turn around for a second attack. You want to time your second attack so that you are reengaging the enemy just as your cooldown ends, thus maximizing your damage. It takes practise. Also, it is better to error on the side of waiting too long rather than not waiting long enough.
Chasing Fleeing Units
Like all units without firing animations, Mutalisks can attack while remaining at full movement speed. This is the origin of the term "dancing", although it has become diluted and is now usually applied to Dragoons. Simply issue the attack command followed instantly by the move command. One thing to note is if you do not give the Mutalisks a target, they often decelerate before firing. If you are chasing units that move at the same speed (Mutalisks, Corsairs, etc.) this will cause you to let them slowly get away. This is why you must target a unit rather than attack-moving.
Dealing with Latency
Latency is the time between when you issue a command and your units react to the command. You will notice on LAN or Hamachi, units respond instantly to commands, while on Battle.net there are slight delays. Normally these slight delays are not an issue, but when trying to execute difficult Mutalisk targeting, you should alter your game play and strategy to account for latency.
Every command you issue has to be before you need to happen. This means if you are targeting Marines, you actually need to tell your Mutalisks to run away before they have fired. Getting the timing down with Latency can be nearly impossible, meaning you should adjust your game accordingly in the following ways:
- Don't target Mutalisk-killing units.
Without Latency, Mutalisks can easily target Marines in groups or even Archons. You would be wise not to attempt these manoeuvres with latency. For every time it works, I would wager it will end in disaster 2 or more times.
- Don't overdo your dancing
Earlier I suggested that you always keep your Mutalisks moving at full speed to avoid ambush. Well, now I'm suggesting you don't do that with latency involved. When you're fighting a single Turret or a Cannon, just stay and kill it. When you find an undefended worker line, just sit there and target the Workers individually, rather than weaving in and out.
Remember that while your Mutalisks are alive they are dealing economic damage (you are expanding while he cannot move out) and also dealing psychological damage (frustration). Don't give this up trying to be a hero against a group of 24 Marines.
The plural of Scourge is Scourge, not Scourges (just like Templar -> Templar, not Templars). Die if you say that. Depending on the latency and your skill level, there are a few different ways to handle Scourge.
First, you never want to leave your Mutalisks idle in vision of enemy units, as this will allow your opponent to easily clone his Scourge against you. Ideally you want to be engaging the Scourge, forcing your opponent to try to clone them quickly, and increasing the chance that he makes an error.
That being said, Scourge lose their effectiveness as Mutalisk numbers increase - cloning them becomes difficult at high numbers and they are more likely to die from Mutalisks' bounce damage when moving in. If you find yourself ahead against a heavy Scourge user, you are better off building up your Mutalisks and then engaging.
When fighting an army of Mutalisks and Scourge, you want to bait the Scourge by engaging the Mutalisks. As soon as you see the Scourge approach, being your retreat, while focus firing backwards to eliminate the Scourge. Once they are gone, reengage the lone Mutalisks.
If you are getting chased by Scourge you have two options. The easiest is to try to figure out which Mutalisks are targeted by the Scourge, by sending them on different paths and seeing where the Scourge go. Once you know which Mutalisks aren't targeted, you can bring them back to fight while the targeted ones continue to run. Secondly, you can try the "Chinese Triangle" which was discussed in this link http://teamliquid.net/forum/viewmessage.php?topic_id=51214 . I'll try to explain it with words but it might not come across, I encourage you to watch the video in that link if you want more information. Assume your Mutalisks are running east. You want to tell them to move in three different directions, essentially drawing a triangle. The first will be a 90 degree turn, so either north or south in this case. Let's assume north. Your second click is back towards the direction you were heading, but 45 degrees past. So in this example, you were flying east, then went north, and then went southeast. Your final click is back towards the direction you were running from, west in the case. So the entire manoeuvre is E, N, SE, W. If you do this properly, and very quickly, the Scourge screw up and spin back, giving you time to snipe one and continue running. Rinse and repeat. I pretty much do not advice you try this method ever, but it's included in this guide for posterity.
There is some minor debate about attack-move versus patrol when fighting Scourge. The general consensus is that patrol works better if it is placed properly (close to your Mutalisk group). I personally always use attack-move.
I am inexperienced with executing fancy micro against Scourge. There are a few ideas about killing Scourge in this thread (pages 2-4 specifically). You should read the advice offered there and test it on your own. I will mention, again, that if you have the advantage against a Scourge user, things will be much easier if you simply amass Mutalisks before attacking rather than engaging with a low number of Mutalisks. Mutalisk against Scourge micro is among the hardest in Starcraft, and the latency of Battle.net does not make it any easier.
Upgrades are a difficult part of Zerg play. First off, in Mutalisk versus Mutalisk battles, Carapace is always the best upgrade to get. If you can afford it, three carapace upgrades before any attack upgrades is preferred. When a Mutalisk fires, its damage is divided by 3 every bounce. This begins at 9,3,1. When you upgrade attack, this becomes 10, 3.33, 1.11, essentially an increase of 1.44 damage; however, when fighting an opponent who instead upgraded carapace, each of those hits gets reduced by 1, meaning it would become 9, 2.33, 0.11. The carapace-upgrade Mutalisks are taking 1.56 less damage per attack. If you don't understand, upgrade carapace. Additionally, Scourge benefit from the carapace upgrade, allowing them to avoid dying frmo bounce damage while closing in. It should be mentioned that because damage is counted as either an integer or a half, the numbers won't work out exactly as mentioned above, but it was just to give an example.
Upgrades' effectiveness increases as your number of units increases, so if you are getting a carapace upgrade, you are better off trying to defend and accumulate Mutalisks rather than playing a skirmish style of play. Similarly, if you suspect your opponent is stalling for his carapace upgrade to finish, you want to engage in skirmishes with Scourge and Mutalisks. If you are playing a map conducive to fast expansions and macro, you should begin the carapace upgrade as soon as your Spire finishes. If you are playing a more aggressive map, I would avoid the upgrade until you have at least expanded.
It is worth mentioning that some players have said that the cost differential between the second carapace and first attack upgrade make it more reasonable to upgrade attack rather than carapace as your second upgrade. While this may be true, if you are playing a game that is going long enough for you to consider a second upgrade, your Mutalisk numbers should be large enough that one less Mutalisk while you research the second carapace upgrade should not matter. If you are trying to punish your opponent while you have a carapace upgrade and he doesn't (much like Protoss does to Zerg while +1 weapons is finished before carapace), do not research a second upgrade. Time your attack to be maximized as soon as the upgrade completes.
As unlikely as it is, upgrade carapace against Hydralisks. Mutalisks are meant to take damage while Zerglings deal the damage. It should be noted that many players have said that they prefer getting Mutalisks attack, while helps in raiding, sniping stray Hydralisks and dealing with Spore Colonies. I disagree; I believe that carapace is necessary for allowing your army to live long enough to let Zerglings engage the Hydralisks and start dealing damage.
To group with an Overlord or not? Let's discuss the pros and cons of each. If you group with an Overlord, your Mutalisks are easier to control when you are targeting and raiding. They are much harder to Scourge. However, you are more likely to lose that Overlord in this matchup. Losing an Overlord is actually a fairly big deal in Zerg versus Zerg. Also, when you get in large Mutalisk battles, the ones that stay clumped together tend to lose to the ones that fan out around them. I have no idea why, but from my experience, that's what happens. What I personally do is group them with an Overlord at the start of the game, and as our groups become larger, I'll ungroup them.
You should always focus fire when getting in small Mutalisk battles (less than 20). A dead Mutalisk isn't hurting you; several hurt Mutalisks are. In this vein, your groups should contain at most 7 Mutalisks, since 7 * 9 * 2 = 126, meaning you will kill a Mutalisk in 2 shots and not waste any damage. If either of you had upgraded, adjust accordingly. Once your numbers get larger than 20, forget about this and just group everything together. Once the battle starts you should focus more on bringing in reinforcements and Scourging properly.
Overlords soak up Mutalisk bounce damage (they take damage that otherwise would have been dealt to a Mutalisk). Is this going to make up for the fact that he has 10 more Mutalisks than you? Of course not. Will it tip the balance in your favour with equal numbers of Mutalisks? Yes. It doesn't warrant getting the speed upgrade to use this tactic, but it is something to remember, especially in the case of close positions (Paranoid Androide, Lost Temple, Python). Keep in mind that Overlords benefit from the crapace upgrade as well, allowing them to soak up more bounce damage before dying. This is especially important in big, end-game Mutalisk battles.
The most obvious use of Mutalisk harass. I really don't have much to say here that isn't already known by everyone.
I would say eight is ideal. Eight is enough to kill Missile Turrets quickly (as discussed in the opening section) and to one-shot Marines and Medics. Often times you will end up with nine Mutalisks simply because you have three Larvae at three Hatcheries. Once your numbers fall below 4, you can no long snipe Marines and need to change your game plan to killing SCVs or simply being annoying rather than targeting the main army.
Should you rebuild Mutalisks or build more than eight (nine)? This honestly depends on the flow of the game, but the simple answer is no. Once you've hit nine Mutalisks, you don't need anymore, and building more than that won't help much. If you opened with a two Hatch build, you may want to add Mutalisks, simply because two Hatch builds generally require great damage to make up for their lack of economy. If my two Hatch Mutalisk build was dealing damage and my opponent had no Turrets, I would make non-stop Mutalisks. If he had 4 Turrets up per base and a small army, I wouldn't bother - the economic damage has already been dealt by forcing him to make Turrets. Adding Mutalisks isn't going to deal any more damage.
Don't upgrade Mutalisks, it's not worth it. In the unlikely event you are fighting Terran metal, upgrade carapace.
Your target against Protoss is undoubtedly the Probes. Cannons are not strong against groups of more than 8 Mutalisks, so don't fear unprotected Cannons. Once the Cannons are dead, target Probes while dodging Archons. Keep an eye out for fresh Templar warping in that can be easily picked off. Don't bother with hearty buildings like the Templar Archive. If you had enough time to kill a building like that, you've only let the player come back into the game, as he has undoubtedly added several Cannons to his supply lines now.
Over Battle.net, you generally shouldn't do it. But there are a few times when it's not a bad idea to go after an Archon, and I'll break these into two groups:
The first, is engaging an Archon. You would want to do this when the mineral line is well defended, but the main base isn't. If you can kill the roaming Archon, you have free access to kill Gateways and tech buildings, as well as any new Templar that warp in. To do this, simply spread your Mutalisks as much as possible and engage. I always like to send one Mutalisks in first and run it past, ensure my grouped Mutalisks aren't taking splash damage until I have them spread. Obviously any decent player is going to target a clumped group of Mutalisks, so get them spread as soon as possible. If the Archon begins to run, give chase, while avoiding clumping back up again.
The second situation is sniping an Archon. This works similarly to fighting Marines - fly straight at it, fire and retreat before entering the Archons range. You can do this at any time, but it only makes sense to do it from above a cliff or when the Archon is having trouble getting through a Probe line.
Fighting Corsairs is similar to fighting an Archon head on. Lead with a Mutalisk and run it past the group of Corsairs to allow your grouped Mutalisks to avoid taking splash damage. Spread your Mutalisks around the Corsairs and target them one by one. If you want to be cute, run damaged Mutalisks away and return them to the battle after another Mutalisks has been targeted by the Corsairs. If you are going to Scourge the Corsairs, Make sure the Scourge are either spread out or cloned, and always attack from a different direction than the Corsairs are firing to avoid losing valuable Scourge to splash damage.
Always upgrade carapace against Corsairs.
As I said, if you feel anything at all is wrong or needs a better explanation, let me know. This is a living guide and is definitely not set in stone. I suppose the Terran guide should be longer but it's kind of intuitive and I ran out of steam writing that part last.
http://sc.gosugamers.net/thread/142563 - GG.net thread about Mutalisks against Scourge using patrol.
I will add the Mutalisk micro training maps once I return.