Power Tokens
From Card Hunter Wiki
Straight from Blue Manchu dev diary (needs cleanup):
Our power tokens are divided into levels which we just refer to by colour:
Clear Bronze Silver Gold
In single-player, your character gains power tokens as they level up. At the start of the game, you have no tokens, which means that you can only use items that don’t have any token requirements (there are still plenty of these though). As you level up, you’ll eventually get your first clear power token. This allows you to use one item that requires a single clear power token to use. You can see where it goes from there.
In balanced multi-player we just pick a standard level and give you the power tokens that you’d have at that level.