League of Legends developer Riot Games has announced that the game is averaging over four million players per day, double the player base that it reported just four months ago. This includes a peak of 1.3 million concurrent players, and 11.5 million active monthly players, and 30 million registered players.

Riot also teased "Season Two" of the game's tournament competition, offering a $5 million prize pool. The winning team will get $2 million, and players are encouraged to use the spectator mode to watch the competition.

"The incredible passion and dedication of our players is positively inspiring," said Riot CEO Brandon Beck in the announcement. "Our community's boundless enthusiasm is why they are central to every decision we make at Riot."

"It's staggering to think about the fact that over a billion games of League of Legends have been played since launch," said president Marc Merrill. "In 2012, we intend to deliver even more for our growing audience."

At least some of the game's success can probably be attributed to its free-to-play model, which rotates free heroes every week to give users a taste of them. The constant churn of free heroes to try gives plenty of small tastes, so players can continuously buy new ones. We're seeing more F2P success stories now as the market for large-scale online games moves in that direction, so LoL might blaze trails for others.