Call of Duty Warzone Mobile Season 5 keeps Activision’s pocket-sized FPS titan fueled up with a fresh smattering of content, but the real highlight is what it means for The Keep. Exclusive to iOS and Android players, The Keep is Call of Duty’s way of getting in on the gacha game hype train. If you’re looking for some futuristic sci-fi threads, then you might want to try your luck.