From GameWatcher: “Publisher and developer Ubisoft today unveiled Containment as the newest limited-time mode for multiplayer first-person shooter Rainbow Six Siege. Inspired by the next entry in the series, Extraction, it introduces a new mode, Nest Destruction, that pits a team of attacking REACT agents against a defending team of Proteans, who are able to take the shape of REACT operators.”
Source: N4G PC Rainbow Six Siege's Containment Limited-Time Event Adds Nest Extraction Mode Tomorrow