Middle-earth: Shadow of War
72 Achievements
68-90h
It Came From Within
Start a Conquest with all Warchiefs as spies.
16.8%
How to unlock the It Came From Within achievement in Middle-earth: Shadow of War - Definitive Guide
Step 1: During Act 2 you will meet Bruz who will teach you how the domination ability works and how you can take over other captains minds to use them in your army. Once this has been taught, go out and kill OR recruit the 2 warchiefs of this area. I recommend just killing them.
Step 2: Once they are dead you need to recruit some captains and then in the nemesis menu, command them by selecting and hover over the dead warchief and select Infiltrate. This will now start up a new side mission called Infiltration.
Step 3: Head to the event and watch your captain fight another for the spot of spy.
Step 4: Now the warchiefs spots have been filled with your captains, start the assault on the fortress and the achievement/trophy will unlock instantly.
Here is a video of me doing it.
This achievement is potentially missable, though there is ample opportunity to unlock it.
To unlock this achievement you need to turn all of the Warchiefs of a fortress into spies and then attack it. You do this by doing the mission that is attached to each of the Warchiefs and when given the opportunity dominate the Warchief and have them become a spy inside the fortress. This needs to be every Warchief of the fortress turned into a spy, if you kill one of them it won't work unless you then replace the dead Warchief with one of your followers, so you have to start the conquest with every Warchief spot filled with one of your followers.
The first opportunity to do this is during one of Bruz's early missions where you need to take the fortress in Cirith Ungol. I would recommend doing this straight away to avoid potentially missing it. It is missable in that there are only a certain amount of conquests during the game. There is one for each of the four fortresses you conquer, then during the Shadow Wars during the post game you can intentionally lose a defence and then have to take the fortress back, giving you another opportunity to unlock this, but you can only do this twice for each Shadow war, your third attempt at re-taking a fortress will just be you vs. the new Overlord until you beat them. There are ten Shadow War missions available so this adds twenty potential opportunities to unlock this achievement.
So while it's highly unlikely you will miss it, it is possible to miss or at least make it more protracted than it needs to be if you don't get it during one of the first four conquests to take the fortresses for the first time in each region.
As part of the main quest you will be conquering fortresses; if you don't attempt this before finishing Act 4 your forts can't be retaken, making this missable.
Every region's fortress has Warchiefs assigned to it, often multiple. For this trophy you need to play the missions that draw out each of the Warchiefs and dominate them, once you have done this that captain will no longer be a warchief.
Go into the army screen and command any of your captains with and press over an open Warchief spot to infiltrate it. Complete the resulting infiltration mission and your orc will become a Warchief. You only need a single Warchief to occupy a spot as long as all of the others are empty. I recommend attempting this in Nurnen as that fortress only has 2 Warchiefs you need to dispose of, start the conquest having done this and the trophy will unlock straight away.
I killed both initial leaders by mistake (one of them - while knocking out the operative trophy). I chose a stronger recruited captain and ordered him to take the place of one of the leaders. This started the quest with the pit. I came to the pit, watched as my orc butchered some random After this, my orc took the indicated place of the leader and repeated the procedure 2 times.
That is, at the beginning of the assault, all the positions of the leaders were occupied by my supporters and the leader had little chance. At the moment the assault began, the trophy fell out.