Dota 2 isn't just an ever-repeating, five-on-five race to destroy your enemy's base. Every so often, Valve adds temporary cooperative game modes to the MOBA that unite the toxic player base against an entirely different end goal. In the build-up to The International 7 -- a yearly tournament that's like the Wimbledon of Dota -- Valve has just released the most elaborate of these yet. It goes so far as to call "Siltbreaker: Act I" the first multiplayer Dota campaign, since it plays more like a quest-centric RPG than anything else. Unlike the core MOBA, though, it's not free-to-play.