StarCraft: Brood War/Protoss Mission 6: Return to Char

The scenario
You start with two bases in this mission; a Protoss base and a Zerg base. They are very near each other, so it is easy to support each base when you need to. Once you start the game, you will notice that your Protoss base has many mineral fields, but does not have a geyser. Your Zerg base does have a geyser, but it only has a five-mineral field patch. You need miners from both bases to establish your economy.

Now take a look at your starting Observers; the one on the west side shows you two burrowed enemy Lurkers, and the one on the east side shows you a small mineral patch with a geyser. You have another Observer near your Forge. Lurkers are large-sized ground units evolved from Hydralisks, and they will attack you while burrowed. The Lurkers will probably make you jealous because you can't make them yourself...yet.

You should expand at your small base quickly for more gas. It is ideal to build a Zerg base there, since the area is both closer to your Zerg base and you can get Drones more quickly than Probes. You can support this base with Photon Cannons, but build them up the cliff.

Simple strategy
Your next expansion should be to the west, where it is occupied by Orange Zerg. A group or two of dragoons, hydralisks, or zealots can take it out without too much trouble, but bring an overlord or observer to detect the numerous lurkers located there. Quickly build a hatchery; don't waste your time waiting for the creep to recede. Here, you'll find a bountiful vespene geyser and plenty of minerals if you attack quickly enough.

With the boon of resources coming in from the new expo, build 6-8 carriers with a full capacity of interceptors. While you're making your carriers, make sure your air and armor upgrades are at level 3 and also research Carrier Capacity for extra interceptors.

You will notice that there is a path leading south to the Overmind from your new expo. Once you have your carriers, move them to the new expo and then move them down the cliff to the left of the path. This is because there are spore colonies and groups of scourge which cover the middle and right side of the path. Provided that you stick to the cliff and you don't attack anything, you will not draw any unnecessary fire. Once you get to the bottom of the cliff, the only thing that is standing between you and the Overmind is one spore colony and a handful of hydralisks. Just ignore them, have all of your carriers focus fire on the Overmind, and it will go down in a matter of seconds.

Fast strategy
If you want to try to push to the Khalis as soon as possible, you should follow this strategy. Expand as fast as possible to the second geyser below the zerg base. But you can almost ignore the whole protoss base and everything west of it. Just put enough units/cannons on the west entrance to fight off the occasional few hydralisks and zerglings coming that way.

Now build three hatcheries and keep producing hydralisks; don't forget to upgrade them. Two or three groups of 12 hydralisks each should be enough to push at the brown zerg faction to the south. Send all of the hydralisks produced in your base to support the attack. Then you should be able to clean the winding path to the Khalis crystal with relative ease. Then just send a drone or probe there. This strategy may be faster than going for the Overmind.

Cheesing It
This strategy is for those who prefer to go for the throat instead of fighting your way to the Overmind or Khalis. Focus on building clusters of Photon Cannons, Sunken Colonies, and Spore Colonies to keep the enemy off you while you build. The Protoss Base will be ignored except as a source of income for this strategy.

Build up your Zerg base, and get a Spire and Lair. Research the transport and speed upgrades for your Overlords, as well as max out your Air Armour. Start mutating as many overlords as possible, until you have roughly 60. As few as 36 could work, but it's risky.

Once you have the Overlords with appropriate upgrades, load up at least a dozen of them with one drone or probe each, although it's safer to do 24. Then, slowing down the game speed if needed, send all your overlords to the Khalis, hugging the right side of the map. Try and synchronize them so that all the groups depart as one large cloud, with the Overlords carrying probes and drones in the middle. So long as you have at least 36, some of them will get through, dropping their cargo and winning the mission. If your luck is terrible and all the Overlords carrying workers are killed, reload from before they set out and try again, creating more overlords or workers as needed.

Shuttles can work too, but Overlords are much cheaper in a long run.

Slow strategy: complete destruction
This strategy is if you want to totally wipe all enemy units and structures off the map. This will take at least one hour and will use up a lot of resources, but if you want to follow this strategy, then you are free to do so.

While you are idling in your two bases making upgrades, units, and gathering resources, scout around a bit with your 3 observers. Your next expansion (after the one directly south of your zerg base) is to the west, where it is occupied by Orange Zerg. A group of reavers and dragoons/hydralisks are necessary. The reavers can take out the base by themselves, while the dragoons and hydras are there to provide cover. Then, get a hatchery going. Here, you'll find a bountiful vespene geyser and plenty of minerals if you attack quickly enough. Wait for your resources to start coming in, and in the meantime, warp in a fleet beacon and a few stargates (if you haven't done so already) and ensure that all your upgrades at the forge and cybernetics core are at least at level 2.

When you have a sufficient quantity, prepare your attack force. You'll need 24 carriers; that's right, 24 as well as some secondary units to provide cover against scourge. This will take up over 2/3s of your supply and use up almost all your resources and use up a good amount of time, so feel free to discard any excess units you don't need and try conserving your money.

Once you have the said strike force, send your carriers down towards the Khalis. You will meet EXTREMELY heavy resistance in the form of dozens of scourge and plenty of hydralisks and mutalisks. However, once you break through to the Khalis, the brown zerg will not put up as much resistance as in the start. Wipe out all of brown's structures and then wreck the yellow zerg bases. Destroying all of the zerg on the map will take around some time and get ready to lose almost all your carriers, but if you're careful and patient, you will wipe the whole map clean. Then at this point, it is your choice to either send a probe to the Khalis or kill the overmind.