Play games
Choose the game that interests you and play itfor free.
Complete the quests
Every game has some quests for which you will receive Soul Gems.
Receive rewards
You can exchange your Soul Gems for Steam Wallet top-ups, game keys, CS:GO Skins and other rewards.
Mine was in 2016. I was playing a competitive match in Dust 2 and I got 3 kills with the AK47 followed by 2 other kills with the AWP. I was also the last player alive on the team against all five enemy team players.