Terra Militaris is a free-to-play, browser based massively multiplayer RTS from gPotato. You build an empire by developing and upgrading your city, exploiting local resources to build larger armies. Once you're strong enough you can venture further afield and start meeting up with other players, forming alliances and waging war on your neighbours for their treasure.
As well as managing resources and growing your palace, you can also upgrade your hero, equipping him with new armour and weapons and learning new skills to learn in battle. Fights take place on instanced battlefields and success relies on using your units special abilities well. It's surprisingly pretty and worryingly addictive.
All you need to play is a gPotato account, which can be quickly created on the Terra Militaris site , all it requires is an email address and a username and password. Once the account is activated you can start playing straight from the front page. If you decide to get involved, keep an eye on the Terra Militaris twitter account for information on a series of competitions celebrating the launch of the game.