Tainted Grail: Kings of Ruin is a stand-alone cooperative exploration game set in a dark universe that blends Arthurian legends with a unique vision. Each player controls one of four unlikely heroes who face impossible odds where stronger and wiser champions have failed. Burdened with an impossible quest of finding the One True King of Avalon, Characters set off on mist-covered trails of the island, endangered by depleting resources and challenging Encounters. Their paths soon cross with many enemies and allies, including the three legendary Kings of Ruin, each in their own fallen realm. A system of story flags and evolving Location cards lets players see the long-term consequences of their actions. At the same time, a deep, branching storyline allows them to tackle problems in different ways, ensuring no two games are alike.