Riot Games and American Express will offer a line of prepaid debit cards for League of Legends fans. Does this mean that the popular online game has jumped the shark?

That’s a funny notion, but it’s a serious question. Many games seem like fads, and the point when they get their highest level of popularity in the zeitgeist can also be the point when they trigger a backlash that leads to a decline in popularity. By tying up with American Express in a sponsorship deal, Riot Games has gone mainstream. Riot’s five-on-five multiplayer fantasy battle arena game has 32 million monthy users, and they just might like the idea of having a League of Legends prepaid card.

For American Express, the deal adds some cachet for the brand with the so-called “millennial generation” coming of age now, according to a story in the New York Times. Big brands have trouble reaching young folks these days through television advertising and other media. The cards, pictured at top, are illustrated with images and characters from the game. Cardholders can get Riot Points that can be used to buy characters and other extras. Users receive 1,000 points when they sign up and another 1,000 after loading $20 on the card. About 10,000 points are awarded the first time a card is linked to a direct deposit account.

In League of Legends, which was released in 2009, gamers play for more than a billion hours a month. It has become extremely popular not only because it pioneered the battle arena genre, it is also a big hit in professional gaming tournaments. The cards are launching on the American Express site and on theĀ tournament site for the game on Wednesday.