Shadowbane was/is a free-for-all PvP game. It includes city-building and ressources to compete for. Currently free-to-play and not in development anymore.
I played Shadowbane for about 2 years from the release. Mostly I played a Fury and a Channeler on the Mourning server.
Shadowbane was the first zoneless MMO game I played (yes I know Asheron's Call was first). Sadly the zoneless design was extremely laggy at release and made PvP more painful than usual. The lag issue was resolved after a few months, but at that time most of my guild had already left.
It was also the first game where players could influence/determine the fate of the server/shard through city building and competition for resources. This was in most people's opinion the strong point of the game.
Meaningful vertical movement (flying) that could be used for combat made also possible fly-by shootings and escape from ground-bound forces.
It also had different rulsets and maps on different servers, which could be theoretically changed dynamically (xp-bonus / death penalties).
Another feature showed first in Shadowbane were what is now called "Veteran Reward" allowing players access to additional races depending on their cummulative subscription time.
Immediately axed Design Features
1.) Cross-Shard Travel
Originally there were plans for cross-server travel enabling players to invade other servers. Especially due to the different rulesets and maps it would have been extremely interesting.
2.) custom designed quests
Due to the non-existance of quest NPCs originally plans where for GMs to give players quests, but this was dropped within the first days post-release.
Shadowbane was released for Mac and Windows-PC at the same time. All expansions were also released for both platforms at the same time. In addition both clients used the same servers.
Shadowbane introduced me to a community that was mainly interested in personal gain by whatever means. Rules/Bugs were used for maximum effect possible and random ganking was common. As example siege times were picked to inconvenience the defending force as much as possible (as in 5am CET), and gold/items exploits were used to gain upperhand in conflicts.
On the other hand close-knit groups existed who managed to not only survive but even do a bit of roleplay on Mourning. Other servers had cases, where one guild owned all cities and moved on to other games due to having "won".
(picture from gamasutra.com)