Gates of Hell (Achievements) | Campaign - Final missions SC II: WoL Guide
Last update: 11 May 2016
Gates of Hell:
Build a 100 Supply Army, Destroy the 3 Nydus Worms.
The Big Bang Cannon:
A piece of cake. You will pass by the four Spore Cannons as you leave your base to save the pods. Two others can be found on the way to the infected Terran base, which you will visit either way. The exact locations are marked above (green dots). The Cannons themselves aren't very dangerous, so just attack and destroy them.
Dominion Roundup:
I assume you've already read the mission's description and you know where and when the pods will land. You have to reach them before the Zergs do and you better head out for them when only you receive proper information.
Considering that it's hard difficulty, you should rather quickly make sure you have a proper defence, as the Zergs will keep attacking with increasing force. You will get the Factory with the third drop, but I'd suggest investing in it earlier on, as vehicles will make dealing with the Zergs blocking the way to the pods easier.
Keep on checking if there are any new mercenaries available, as investing in them under these circumstances will surely pay back. With the fifth one, you will get a Starport. With the seventh, the difficulty will increase.
Just as I've mentioned in the description before, the last four will come in pairs. Additionally when you reach one of them, the Zergs will automatically attack the other one, so the best solution would be creating two separate groups and trying to get to both at the same time. However it's no mystery that such a solution is rather risky, especially on hard. Fortunately, there is also another way.
Once you get the Starport, construct two Dropships. After getting the information about the pods, send both transporters with, for example, SCVs, to both destination while trying to avoid enemy units. It shouldn't be too hard, as the area is rather small, but you can save your game before heading out. The "activated" units will of course quickly die from the Zergs' attack, but at least they will count as being saved. Of course you can also try and save a couple of them and take them to your base onboard the Dropships. Remember that the achievement doesn't require you to complete the whole mission.