There are 16 alien signs in the desert. Most of them are along the path you need to follow, only two or three are a little out of the way. When you look at this map, everything seems to be in order except the tower on the right. It seems to be missed placed. If I'm reading this right, it would be further to the right and higher.

The map is in the first settlement you see when you enter the desert (Site A). Most of it map is correct except the most western radio tower. It seems to be missed placed. Also, there are a couple of sites that do not appear on the map but I included them here.

There are three signs in the first settlement you see. You must decrypt all three signs in order to read them. The first two will give you symbols, letters, and numbers. The third will translate the sign to your language. Make sure you go back and read the other two signs that didn't get translated.

If you follow the story, you'll take ANI back to the forest. Eventually, you'll have to go back to the desert and the portal will drop you off on the path to the first tower. Look to your left, there should be a small village. There are two signs there.

This settlement is almost in the middle of the map. If you're following the story-line, then you just came from the western tower where you had to fix a Communications Array. On your way to the final tower, you should pass by Central city. There are two signs there along with two groups of tumblers.

This is the last tower. If you are facing south, there is a settlement to your right and the tower to your left. In that settlement, there are two signs. The third sign is in a building with a spotlight on top of it. That building is next to the tower itself.

Settlement:

Building nex to the Tower:

When you're done at the Radio Station, proceed to the plateau that TR2 was talking about. Before you go the plateau, you'll see a large village up ahead and to your right. This is the largest of the settlements, so it seems fitting that it would be the capital. You'll want to turn the spotlight on since there are six groups of tumblers roaming about. Once, the tumblers are busy playing in the light, you can read the two signs that are there and gather any supplies you may need.

Now head up to the plateau, it's right next to the graves. When that's all done, there's a village to the east of the plateau, above Capital City. There's a sign painted on the side of one of the buildings. Take care, there are four groups of tumblers here.

To the North East, there is a portal, several ruins, and a house all by itself. Inside that house, there is a message painted on one of the walls.

Backtrack to Capital City. Once there, to the South East, there's a path that leads to the Dune Sea along with a sign, After you've read that sign, go into the Dune Sea, there's a hollow wreck straight ahead with a portal that will take you to the last sign. You can see the wreck in the background of this picture.

After you walk through the portal, you will be dropped off in the Remote Village. This is the last sign in the desert. After you read that sign, you can leave assuming you've collected 12 units of Tertium .

Contrary, to the desert, the Cave is much easier. There are four signs here and assuming you did everything right, you'll obtain this achievement.

There is two signs on the path to the main cave.

This sign is in the main cave itself.

The last sign is next to the mine tracks.

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