Bakugan: Defenders of the Core

Gate cards occasionally appear in place of power-ups when things are destroyed. When they do, the environment changes to the element of your Bakugan. So, if you are using Dragonoid, gate cards will always be Pyrus. You need to activate a gate card with a Bakugan of each attribute type to unlock the trophy.

In my experience, gate cards appear more often from destroyed Vexos crystals than destroyed buildings. A couple of USA stages have tons of Vexos crystals, and that is the perfect place to farm gate cards.