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.
I got a key from one of the Gamehag giveaways, but it doesn't look it's a Steam key. Is there anywhere on the site I can redeem it?