The League of Legends started as a free online video game in 2009. Today, it is the leader of a growing e-sports business, with hundreds of professionals players on salary and nearly $1 billion in projected 2014 revenue for parent Riot Games, based in Santa Monica, Calif. The game’s fourth world championship – called the Summoner’s Cup – is slated for Oct. 19 at a soccer stadium in Seoul, South Korea, with 40,000 fans expected to attend and millions tuning in online.

LoL’s popularity is driven by a demographic that skews male 15 to 25, according to a New York Times story. More than 67 million active monthly players worldwide take part. The battle game, which takes cue from “Lord of the Rings” in its design, offers players characters called “champions” as in-game premium buys for under $10. In August, players spent $122 million on this feature, the NYT reports citing data from market research firm SuperData.

SuperData figures suggest LoL is a run-away leader with eight times more players than Dota 2, the next rival in a gaming genre called multiplayer online battle arena. Players download the game from the web and its free to play, and doesn’t require additional hardware besides a keyboard and mouse.

Riot Games was founded in 2009 by three entrepreneurs from the Los Angeles area who shared a passion for gaming. According to the New York Times, the start-up capital came from “about two dozen angel investors from Benchmark Capital and FirstMark Capital” and totaled around $18 million. The company now employs 1,500 people, most of whom are based at the firm’s Santa Monica, Calif., headquarters and some at satellite offices.

In addition to the Summoner’s Cup and other offline events, Riot Games plans to open an online merchandise store next year and offer nearly a million pieces across 40 to 50 categories, from T-shirts to track jackets.