Cards is a big part of FORCED SHOWDOWN, and it adds a very interesting strategic layer to it.
You might think, WTF - cards in an action game, have you been drinking glue for several weeks!?
Well the idea of cards came from the thought that in Rogue-likes everyone fancies a random surprise, but what then - when it's a highly competitive Rogue-like?
Well, we definitely still want some randomness, but how about adding a bit of control to it? - by allowing the player to influence it a bit. So now when you head to battle you select a deck of your desired perks, abilities, spells etc. and thereby you enable quite a bit of strategy in your play.
Example of one of the powerful high cost cards.
The way you use cards is simply by spending Mana to play them during a match. Mana is rewarded when surviving an arena - hence you get a good ton of interesting choices during a match.