Four Kings One War looks like chess at first glance, but it's a much more complex game with a serious learning curve. If you're interested in trying it out without having to pay a dime, the game is free to keep on Steam right now.
Supporting one and two players, Four Kings One War features four different armies on a single board, and you have control of two of them. This means you can make two moves rather than one in each turn, splitting up your armies and potentially attacking from a direction your opponent isn't expecting. It means the normal strategies and tactics used in normal chess are no longer sound, forcing even experienced players to practice.
There are multiple environments to choose from, as well, and you'll see spirits appears and do battle when you make moves. Every move counts, as you can quickly have your own pieces overwhelmed if you aren't careful to protect them.