Skirmish18+ NSFW

Skirmish is a real time strategy card game where you use cards to summon units to fight each other. Each player has two flags for (some of) the enemies to target. Whoever loses both flags loses. If too much time goes by, the flags start to go down themselves and whichever player is still standing wins. 

Skirmish has plenty of customization options. Controls, volume, the size of the menus, decks, and the way your player looks can all be changed. The game itself can also be tweaked like the length of the game and the number of cards each player can have.