While Microsoft didn't offer any information on upcoming products, the move is seen as a signal of Microsoft's growing interest in subscription-based online games, an emerging but profitable business segment.
Sony's "EverQuest" is one of the biggest successes yet, with hundreds of thousands of subscribers paying $13 a month to access the game's virtual world.
But the field is expected to get much more crowded this year with the release of online games geared to more mainstream audiences, including an online version of Electronic Arts' smash PC game "The Sims" and Sony's "Star Wars Galaxies," both of which will be previewed at next week's Electronic Entertainment Expo trade show.
Microsoft has several subscription-based games on its Zone gaming site, including the role-playing game "Asheron's Call."
San Diego-based Sigil Games is run by Brad McQuaid, one of the co-creators of "EverQuest," and Jeff Butler, producer of several "EverQuest" add-ons.