There was a good solution up for this, no idea why author took it down. So here are the results of my research.
My team: Jago, Riptor, Orchid Supposedly any character can work but I wanted to minimize other quests showing up. NOTE: User Rafael D Arroyo mentioned he had better luck with Glacius, Sadira, and Eyedoll (eyedoll must be unlocked via Shadowlords). YMMV and it may simply be RNG but if you are struggling with my three characters perhaps his three are worth a shot.
Step 1 - Acquire 5 stalker transceivers. You acquire these by doing the Stalker Attack missions in South America. Start up a playthrough and fight through missions until you get to around turn 10 or so. You can 'deploy' or just skip turns with Y, but in my experience the stalkers tended not to show up when the corruption was high. Fighting through every fight (or deploying successfully) to keep corruption low saw them show up around turn 10 or so relatively consistently. When my corruption was high a couple of times they didn't show until around turn 20 or even later. Look for a mission in South America with two Riptors as the enemies (regular, not mimmic). The text of the mission should mention two stalkers terrorizing a village. Complete the fight and choose "agree to help
" from the two options after it is over.
This will spawn two Stalker Attacks quest missions the following turn, again in S.America. Complete both of them, choosing to attack the stalker (top option) pre-fight, and examine the device/examine the corpse (top option) after the fight. Each of these will get you ONE transceiver, for a total of two. After this, just restart the game by creating a new team. Repeat the process to get two more, meaning you have a total of 4. Start a new playthrough once more. Once you get to the Stalker Attacks, you will get your 5th transceiver. This will give you the quest mission to attack the stalker hideout the following turn.
2. Attack the hideout. DO NOT choose the option to call in an air strike or mortar strike or whatever. That ruins the quest and you will have to get the 5 transceivers again. Choose the top option pre-fight, search the facility
. After the fight this first time, make sure to choose the option to search the incubators
(NOT the computers yet!). This will get you the Wyvern-X quest item. Here is what the fight looks like on the map screen pre-fight.
3. Continue playing until you get a fight talking about the rebel alliance. This isnt't necessarily in South America. Mine was in Europe as you can see below. Complete it, and you should get an option to give the Wyvern X to the rebel commander in exchange for the Security Codes quest item.
4. Repeat step 1 (starting a new game 3 times to grind out 5 stalker transceivers and get the quest/fight back at the stalker hideout again).
5. Attack the hideout once more. Remember to choose Search the facility pre-fight
. This time, choose the option to Activate the security console
(orange option) after the fight. This option only shows up once you have obtained the security codes by trading the Wyvern-X to the rebel commander. Choosing this option will net you the achievement.