Each player is a mage of one of twelve houses of magic. The goal of the game is to capture your opponent's Sanctum. You do this by recruiting warriors and archers from your fortress and from surrounding towns, and sending them across the gameboard to do battle with your opponent's men. Each of the mages has a deck of spell cards to alter the course of the game by summoning monsters, strengthening or weakening recruits, giving recruits special abilities, changing the squares on the gameboard, etc.
To play Sanctum simply download and install the game, create an account on the author's server and get your free starter pack of cards, enter the Great Hall, and find an opponent.