War! Death! Destruction! Plus cool magic spells and espionage and, eh, diplomacy if you're into that stuff I guess. All this and more is available for free in Dominion, the best in browser strategy games I've found on the net.
Tons of races, tons of strategies, tons of spells and black ops, and a whole lot of invading. You take on other players in a bid to become the biggest and the baddest Dominion in town. You've got 50 days to become the best. It's a lot of fun, I fully recommend it.