Do you remember that one episode of Adventure Time where Finn and Jake play a game called Card Wars? Well, that's a real mobile game now.
It's pretty much everything you'd expect based on the rules from the show, and it actually functions very similarly to Hearthstone. There are four "rows" on the game board, all of which can be filled with various structures and creatures. Each row can house one creature, and rows will be do battle with each other unless it's empty -- in which case, you can damage the "player" and potentially win the game.
A lot of the humor from the show is injected into Card Wars, and the game actually features a surprising amount of voicework -- so it's not just a cheap cash-in for the sake of it. There's even a campaign mode with a sense of progression, and with a ton of different cards to sift through, there's a lot of content to play.
Of course, given the fact that it's card based and every card game needs IAP these days, it's there. It's not offensive in the sense that it feels necessary to play, but if you want more cards you will have to either wait for a bit to earn the cash or just pay up. Be warned -- there is an energy mechanic, however.
Card Wars isn't really all that exciting, but if you're into card games on the go this could be a great distraction.