Diablo has the classic, top-down action that has you dashing between groups of enemies, unleashing your skills to devastating effect. Risk of Rain has that frenetic, wave-based horde survival with a gorgeous sci-fi aesthetic. But what if the two were to collide? The result might look something like Gatekeeper: Infinity, a new indie roguelike with up to four-player co-op that’s just arrived as a free Steam game.