The struggle against the Ancient One takes the investigators out of Arkham and into the darkest corners of the globe. But the aeons-worn ruins of pre-human civilizations hold nameless horrors against which even the miracles of modern science offer little protection... The Door to Saturn is a fan-made expansion for the Fantasy Flight Games board game Arkham Horror. It's a fan expansion, so players need to print the components themselves. The expansion doesn't really have anything to do with the planet Saturn; it's just a good name. The expansion adds new Ancient Ones, items, spells, allies and monsters, as well as a new item type - Scientific items. The expansion also introduces the 'Expedition variant', in which Arkham's supply of Clue tokens depletes as Clues are spent, and the players have to venture on to an Expedition mini-board to replenish the supply. The four Expeditions included are "Antarctica", "Arabia", "Oceania", and "Mars"; taking inspiration from Lovecraft's At The Mountains of Madness and The Nameless City, Abraham Merritt's The Moon Pool and Clark Ashton Smith's The Dweller in the Gulf and The Vaults of Yoh-Vombis - among many others.