Make sure you have a coop partner to complete all 6 chapters over xbox live.
This is a very glichy achievement. We both didn't get the achievement after completing the game in coop. After searching the internet, a solution popped up:
- Make sure you still have some ignite ammo
- Return to chapter 4 scene "the catacombs"
- Go back to the place where you found artifact 1 (Pilot's goggles)
- Shoot the red roots to pass and pick up the artifact
- Thadaaaa achievement unlocked
Very odd indeed BUT it did work!!
NOTE: You both have to finish the game on xbox-live from chapter 1 till 6. If you didn't get the achievement after completing, you can do it this way.
We also found ALL the artifacts in the game so keep this in mind while attempting this achiev.
Edit: We replayed the last part of level one called: King's Barrow. My coop partner got it and I didn't. (We both completed the game form A to Z.) We tried it again and for some strange reason it popped when I jumped the lava pit. Odd but great to have it. Maybe this will help others whi struggle with the same problem. Credits to McD76
Edit: 8Jun13 Can confirmed the googles method worked. My son and I beat the game nothing. Got the googles and burn the game. Note, my son didn't have all the collectables he stiil got it. I had them all but on our game we weren't collecting anything. Credits to MAIZCORN.