Rainbow Six: Siege has been lighting up the charts since its launch almost two years ago, maintaining a loyal player base with a steady stream of new content. The intense multiplayer shooter that bears Tom Clancy’s name has been a rock solid success for publisher Ubisoft, and it is about to get a new mode that is sure to keep people hooked for at least another four weeks.

According to Rolling Stone, Ubisoft announced the third year of Rainbow Six Siege will include, among other things, the game’s first ever co-op game mode, called Outbreak.

When is the Rainbow Six Siege update release date?

The mode update will be playable for four weeks at some point during year three, though Ubisoft did not specify exactly when that would be. Outbreak will include exclusive cosmetic items you can only unlock during those four weeks. Ubisoft said the full reveal of Outbreak will happen at the 2018 Six Invitational event in Montreal. The eSports-focused event runs from Feb. 13 - 18 next year.

More importantly, Ubisoft did not clarify what, exactly, Outbreak will be. The name, combined with the image on Ubisoft’s official website, seem to suggest it could be similar to the co-op Zombies mode that has been so popular in Call of Duty since 2008’s World at War. Rainbow Six: Siege is a competitive shooter centered around completing objectives in smaller, highly destructible environments, so perhaps it could be a mode in which four players try to protect a building from a horde of zombies, mutants or anything else that would be fun to shoot.

This is just the latest development in what has been a surprising level of long-term success for Rainbow Six: Siege since its launch in December 2015. The initial version of the game reviewed decently and had its fans, but the amount of microtransactions it had on top of being a fully priced $60 game was divisive at the time. Still, Ubisoft stuck with it, regularly adding new content and addressing fan concerns over time. That work paid off, as Rainbow Six: Siege hit an astounding 20 million players in August.

Year three of Rainbow Six: Siege will add more than just a temporary new mode. According to Ubisoft, it will feature eight new playable characters and two new maps. If you have not gotten into Rainbow Six: Siege yet, IGN reports a number of outlets will have it for $25 as a Black Friday 2017 deal.

Despite the success of games like Rainbow Six: Siege, Ghost Recon Wildlands and Assassin’s Creed Origins , Ubisoft still finds itself in the crosshairs of corporate takeover talk on a frequent basis. The independent French gaming publisher has most recently been seen as a target for fellow French media giant Vivendi, though Vivendi temporarily backed away from takeover rumors last week. Aside from the obvious motivation of wanting to sell as many video games as possible, this speculation possibly gives Ubisoft even more motivation to make sure games like Rainbow Six: Siege are as successful as possible for as long as possible.