Lord of Knights invite code 'inviteen'. Enter the word: inviteen and get a rare card and extra gold! Just hold and copy the code below: Inviteen
It's out in New Zealand so it should be out in the US very soon. Tested the Lord of Knights referral code 'inviteen' and it works perfectly - gets you 500 CP which means you can draw some of the best cards.
Since we are currently having an event that need referral codes. Players of Lord of Knights: The Conquerors can post their referral codes here.