It is the kind of card game where you are a magician and use creatures to damage your opponents. It is nice and it is free. Well, if you want a better card set, you will have to buy it, but it is possible to live with the begginner's one. Your first deck is randomly defined by the game, and I got an incredible one there.
Site address: http://www.alteil.com/
Time spent playing: as much as you want. A game takes from 30 to 60 minutes though.
Free: No ads, begginner's deck is free.
(This game was Discontinued)