Skulltaker Halo: CE: Recession
From Halopedia, the Halo wiki
Skulltaker Halo: CE: Recession
Skulltaker Halo: CE: Recession is an achievement in Halo: The Master Chief Collection. It is awarded for activating the Recession skull in Halo: Combat Evolved Anniversary remastered mode on 343 Guilty Spark. The achievement is worth 5 gamerpoints and can be unlocked on any difficulty.
Location
The skull is located to the left of the facility in a little drop behind a shade turret. When the player crosses the fallen tree, they'll see a shade turret blow up and assault rifle fire coming from the structure. Instead of going inside, immediately go to the left and keep against the back wall. You will come to a turret with a small drop behind it. Slide down the drop carefully; the skull is at the bottom.