A new code for unlocking Mythgard's Core set has been revealed via Pocket Gamer. This code will unlock Aztlan's full core set of cards!

The code is PocketGamerAztlan.

This is the fourth code for the game, here are the others:

You have until March 15 to redeem the code, so what are you waiting for? To redeem the code, go to the Store tab, and press the Redeem Code button. iOS users will have to use another client as code redemptions are not available on that platform.

Quote From Rhino Games

We know it's been a little bit since our last code, but don't let that make you ANY less excited for this one! This is code number 4 and we are ecstatic to share it with you!