Head over to east of Keryev, you will find a little Stonehenge looking thing in between Keryev and St. Petersburg. There is the Soulcrystal symbol and a note on the ground. There is a bone in the middle of the Stonehenge, too... pick it up, you might need it later.

Needed:
A gun with enough ammo to kill around 20 zombies
A horde beacon or something to draw zombie's attention
Flashlight or Nightvision

Optional:
A turret with a gun to go in it
1 or 2 medkits

Head to the St. Petersburg Metro Tunnel, either one will do. Once you made it to the area with the train tracks, turn right, and follow until the end. On the right wall you should see the same sysbol you saw at the Stonehenge. Press "K" (or whatever button you use to open area chat) and type "Anastasia" (make sure it's night time) you should see the wall to the right of you raise... revealing the crystal.

Now, place your Horde Beacon or lure in the zombies, and get killing! Remember: you MUST kill the zombies INSIDE the crystal room, or else "the souls won't be collected".

After activating the Soulcrystal, you will be teleported to a research facility... a Scorpion-7, Research Facility. in the basement you will find another soulcrystal, touch it, and you will be teleported back to St. Petersburg, and get the achievement.

This was "Part one" of how to do the 2nd easter egg in Russia. Click here: https://steamproxy.net/sharedfiles/filedetails/?id=1419312726 for a guide on how to complete that.