StarCraft/Protoss mission 6: Into the Darkness

From beginning to the Protoss Teleport Beacon
This scenario is a lot more difficult than the other installation missions you've played so far. You get less units, a weaker hero (at least compared to the stuff you face in the mission), and much more enemies and traps to fight through.

You start in the upper left corner of the map. Just follow the path for a while, using your Zealots to easily dispatch the Hydralisks and Zerglings that stand in your way (by the way, your Zealots are equipped with the leg implants, and are fully upgraded to level 3 in weapons, armor, and shields even if you neglected to do so in the previous mission). Soon you'll come to some stairs; descend it to the lowered area, and proceed, being careful to stick to the upper wall of the room. This is because there's an Infested Terran lurking in the area above the lower wall (the first of many), and if he sees you he'll come down and attack. At this point in the mission, you have no useful ranged units (Tassadar has a ranged attack, but it's hardly more than a Mutalisk's range), so it's tricky to take these out before they explode. As you play this mission, remember that these Infested Terrans deal 500 damage, which means Tassadar can be killed in one fell swoop (explosion, rather). More information on how to avoid this later.

Go into the next room and go slightly north. Among the grisly remains (get used to them, by the way), you'll find a team of five Marines, sitting around and willing to give you a hand. You have a choice here: if you take them along, you will have a significant boost in firepower (and these are not the only Terrans available on the map) and therefore will be able to make it through most of the mission more easily, but the Marines will also trigger some traps along the way that cannot be triggered by your Protoss units. These traps usually consist only of several Zerglings and Infested Terrans, though, so it's probably a better idea to just take them along. As you fight with the Marines, remember that they don't have regenerating shields like your Zealots, nor do they have friendly Medics such as in Brood War; therefore, try to have your Protoss units take damage for the Marines if at all possible.

In the southwest corner of the same room, you'll find some burrowed Hydralisks. You could take them out with the Zealots and Marines, but it's much easier to just Psi Storm them away. After they're dead, continue through the door they were guarding (yes, this is a detour, but it's worth it). After dispatching another set of Hydralisks, you'll find four more Marines in the room at the end. Add these to your party and go back to where you found the first five Marines; from there, start again to the southeast.

Now that you have ranged firepower (assuming that you're taking the Terrans as you go), you have ways to get around things. Take the next door that you come to, for example: on the other side, three or four Zerglings are buried to each side of the door. You could barge in with the Zealots, but it's a much smarter idea to lure the Zerglings out by going near their position (without going through the door; just get as close as you can while still on this side), then having the Marines shoot 'em up (they can shoot through doors). Zerg units cannot open doors, so your own units will not suffer a scratch. Rinse and repeat for the other side.

Carefully enter the room. There are some Zerglings and—more critically—an Infested Terran on the far side, and if you don't want to risk massive Marine losses, you'll have to do a similar luring trick as before. This time, position all the Marines to one side of the room (stay close to the door that you came through) and Tassadar on the other. Tell both to Hold Position, then send in the quick-footed Zealots to grab the attention of the Zerglings and Infested Terran before running away. The enemy units will get caught in a crossfire, and if you positioned the units right, the Infested Terran should die before it reaches either the Marines or Tassadar. Refer to the screenshots for more positioning clarification.

Continue down the path, and stop when you come to a split path. One continues the way you were going, and the other (through two doors) leads northeast. As you can probably guess, the latter is a detour for more units. As soon as you go through these doors, you'll get ambushed by some Zerglings; dispatch them and go a little bit further to the northeast, until you come to a wide walkway across the chasm, leading northwest (there are more Zerg where the Zergligns came from, but there's no reason to waste time on them). Go down that path, and kill the Hydralisks along the way. Before ascending the stairs, destroy the turret that pops up with your Marines (Zealots are not good for this, because they have take more damage while taking them out). When you're on the upper level, step on the Beacon with any of your units, and you'll get reinforcements in the form of two Zealots and a Dragoon that appear in the Teleportation Field.

As you backtrack, don't bother going further into the top right corner of the map—it leads to an area that looks similar to the Teleportation Field at first, but actually holds nothing but lots of enemy Zerglings. Just return to the double doors and resume your trek.