How Assassin's Creed III's New Co-op Mode Cranks Up the Pace - Xbox 360 News at GameSpot
Wolfpack is, in a word, fast. You begin a round with a fixed amount of time, and once your team takes out its first target (or group of targets, in most cases) you get more time added to the clock. So right off the bat, there's a strong incentive to keep things moving and string your kills together as quickly as possible.