Siberian Strike DLC
This DLC is a very straight-forward completion - Aside from the collectibles there is only 1 other achievement that isnt story related - That is called Shadow Man and in all honesty its isnt a tough one to get either - So here we go, hopefully you find these videos useful
Shadow Man Achievement Guide - Mission 3 of the DLC - Last Rites
As you exit a building you will see 2 guards walking away - Just after you will enter a really dark area. You need to get through this area undetected.
You can kill the enemies if you wish to - If you get seen just reload your checkpoint and try again