Firefly title beaten only by Valve's Team Fortress 2
Firely studios claims that Stronghold Kingdoms has been ranked second in popularity among free-to-play games on Steam since its February launch.
Kingdoms is an MMO adaptation of the award-winning tactical castle-building games from the London based Firefly.
The game has held the position for three months, fending off newcomers and battling its way into the top ten most played on Steam.
The only title in the category that seems untouchable is Valve's own Team Fortress 2, which has held the top spot ever since the hat crazed cartoon shooter first went free to play.
Firefly says Kingdoms has nearly reached the company goal of a million users since the release of German, Russian, and French worlds, and the game's launch on the Steam platform.