A free app for Android, by Mojang.

Scrolls is a card game with a unique twist: you build your own army of monsters, warriors, and magic users, and battle against other players in real-time online multiplayer games. 

As you build your army, you can deploy your forces by using scrolls, which you can collect in random or sequential order. You can also buy or sell the scrolls you don’t use, and you can trade with other players on the black market.

Once you’re ready, you can battle against other players and compete for first place on the leaderboard.