An expansion launched a couple months ago for card game Magic: The Gathering -- Duels of the Planeswalkers 2013, bringing with it five Ravnica-themed guild decks, each based on a two-colour combination. Now a "deck pack" has been released for the game, bringing with it two more guilds: the Red/White Boros guild (soldiers, buffs, and burn), and the Blue/Green Simic guild (snakes and weird science-y stuff). Hit the source for decklists, and go here to check out the leaked Dimir guild (whether the leak was intentional or not, it's really hard to say given this is Dimir we're talking about).
I've only really gotten much time with the Simic deck, of which I can say it's atrociously boring and weak at first, but becomes progressively more fun and effective the more cards you unlock for it and the more you edit the deck. Boros, meanwhile, seems effective right out of the gate.
The decks are packaged together, of course -- to get them, you pay a reasonable three bucks (though two seems like it would make more sense, given there are two decks, and presumably three more will come in the next pack).