Developer Treyarch has a good record of keeping things fresh in Call of Duty. The company started working on the franchise back in 2005. With World at War it added zombies, Black Ops went to Vietnam, Black Ops 2 traversed time and added branching narratives. For its next installment, Treyarch is, once again, trying something new. Call of Duty: Black Ops 3 (set to arrive November 6 on PC, Xbox One and PS4) brings campaign co-op to the franchise for the first time. The entire campaign will be playable co-operatively by up to four players online (or two players locally). The addition of up to three campaign players meant building bigger combat arenas, better AI, and adding social features for showing off medals and achievements.