Mature Minded Gamers: Rise of Legions - Strategy, Deck Builder, and Tower Defense all rolled into one.

Rise of Legions has done something very cool, it's mixed some of the hottest game types and rolled them into a sweet treat that is free. The interface is easy to use and the game tutorial takes about 10 minutes. So unlike a MOBA that has a steep learning curve you can pick this one very quickly. It offers 4 deck colors and the ability to mix up to 2 colors to create your own concoction. The card unlock system is fair and while it can take some time to unlock all the different cards without spending a penny, it's reasonable and can be done by causal players, which is rare these days. For a free to play game and coming from a 3 person team I'm really impressed and have enjoyed my time with the game, with that said I highly recommend you give it a try.