SEATTLE – A bewitching creature – half woman, half deer – battles a shaman and a sentient tree. Lightning bolts strike. Weapons explode. Nasty spells are cast.

The video game “Dota 2,” like so many across the Internet, transports teams of players from their bedrooms to a verdant virtual world where they smite each other through keyboard and mouse clicks. Except on this sunny day in July, every attack and counterattack by a five-person team set off an eruption of cheers – from the more than 11,000 spectators crammed into this city’s basketball arena.

The contestants were gunning for a big piece of the $11 million in prize money, the most ever at a games tournament. And the game’s developer, Valve Corp., moved another step closer to securing gaming’s legitimacy as a major-league spectator sport.

Having upended the entertainment world – global revenue for games is $20 billion higher than the music industry’s and is chasing that of the movie business – the games industry has turned its ambitions toward the lucrative world of professional video game competition, widely known as esports.

The signs of success mirror the achievements of major sports. Game tournaments sell out giant arenas, and some attract at-home audiences larger than those of top traditional sporting events. Madison Avenue’s highest fliers, like Coca-Cola and American Express, have lined up as sponsors. Prize money has soared to the millions of dollars, and top players earn six- or seven-figure incomes and attract big and passionate followings, luring a generation of younger players to seek fame and fortune as gamers.

Last year, the State Department began granting visas to professional gamers, under the same program used by traditional athletes. This fall, Robert Morris University in Chicago will dole out more than $500,000 in athletic scholarships to gamers, the first of their kind in the United States, and Ivy League universities have intercollegiate gaming. Last week, web giant Amazon announced it was buying Twitch, a hugely popular video streaming service used by gamers, for $970 million in cash.

“This stuff is expanding out of control,” said James Lampkin, a product manager for ESL (for Electronic Sports League), one of the biggest esports leagues, which had 73,000 attendees at a four-day tournament in Katowice, Poland, in March. “We have no idea what the limits are.”

Game competitions have been around for decades, but what was happening at that arena in July would have been unthinkable, even laughable, only a few years ago. As broadband Internet access and free-to-play games have spread, gaming competitions have multiplied in size and frequency around the world, going beyond early strongholds like South Korea.

At the Seattle event, cheering fans, many dressed in costumes to look like game characters, hoisted national flags to show support for their favorite teams. Commentators, known as casters, offered play-by-play. Confetti rocketed into the crowd when the winners were crowned.

More than 70 million people worldwide watch esports over the Internet or on TV, according to estimates by SuperData Research. South Korea even has a TV channel devoted largely to esports. A championship tournament in October for “League of Legends,” an arena battle game, streamed around the world, attracting 8.5 million simultaneous online viewers at its peak – the same as the peak viewership for the deciding game of professional hockey’s Stanley Cup finals in June. This year, the “League of Legends” championship is expected to attract 40,000 to 50,000 attendees to a soccer stadium in Seoul, South Korea.

As the fan base and money in esports have ballooned, multiple independent game leagues have emerged, including ESL and Major League Gaming, that collectively put on dozens of competitions a year. Game publishers host events, too, seeing irresistible opportunities to promote their games.

One of the most ambitious publisher-led efforts is from the creator of “League of Legends,” Riot Games, which operates leagues around the world. For the past two years, another publisher, Activision Blizzard, has put up $1 million in prize money for a championship for its combat shooting game “Call of Duty” in Los Angeles.

“I don’t think we’ve ever seen the opportunities for esports as promising as they are today,” said Robert A. Kotick, chief executive of Activision Blizzard.

Still, for the cycle to continue, the industry will most likely need to overcome some long-held opinions on games and gamers – in particular, that the skills involved are inferior to conventional forms of athletic excellence. When ESPN2, the cable sports channel, ran a show about the “Dota 2” tournament in July, Twitter was flooded with derogatory comments about esports being shown as a sport.

Lampkin of ESL said he wasn’t worried about such attitudes. The argument over whether professional gaming is a sport in the traditional sense, he said, is beside the point now.

“If you don’t want to call it athletics or sports, that doesn’t mean anything to me,” he said. “That doesn’t change the reality of the massive growth we’re seeing.”