Curse Voice launched last year to directly integrate voice communication into video games, including Riot Games' 'League of Legends.'

Curse Voice is competing with other communication programs, such as Skype and Teamspeak, but it has more functionality - including being able to monitor what games your friends are playing and instantly begin voice chat with them.

In a filing with the Securities and Exchange Commission on Tuesday, Curse said that Riot's $30-million investment was just a starting point and more could be invested based on certain milestones.

Last year, Curse received $10 million in Series B financing from GGV Capital.

'Riot really believes in what we're doing and where we're going,' Curse Chief Executive Hubert Thieblot said. 'This investment boosts our efforts to continue creating what I believe to be the best communication tool in gaming.'

A Riot spokesman said the company made the investment to help promote technology development at Curse. But he noted that it was not a partnership.

Curse Voice has grown to more than 1 million active users, Thieblot said.

When Curse Voice launched last year, Riot initially was not supportive of the technology, saying it violated the company's terms of service by automatically connecting players to voice chat and providing in-game information that wasn't available to other players. But Curse quickly worked with Riot to remove or revise those features.