Oerth Oerth , the world of the " Greyhawk " campaign setting , is an alternate Material Plane world parallel to Toril . Inhabitants . Oerth is home to prominent wizards such as Bigby , Drawmij , Tenser , and Mordenkainen whose spells have spread even to the Forgotten Realms . Mordenkainen is an acquaintance of Elminster Aumar ' s ; the two have met on numerous occasions at Ed Greenwood ' s house on Earth to exchange spells and lore . Mordenkainen , when he had newly mastered interplanar travel , used to visit Waterdeep with some regularity . In the book " Passage to Dawn " by R . A . Salvatore , when Harkle Harpell enters into an unorthodox contest of wizardry with the Sea Sprite ' s wizard Robillard , Harkle and Robillard cite a number of Oerthly wizards , including Bigby , Melf , Otiluke , and Tenser . " Robillard blanched despite his own impressive display . Of course he knew of Bigby ! He was one of the most powerful and impressive wizards of all time , on any world . " The Oerthly bard Gwydiesin of the Cranes has also chatted with Elminster on occasion . Both Elminster Aumar and Khelben " Blackstaff " Arunsun have spent time on Oerth , and Elminster suspected that Khelben Arunsun the Younger settled there to begin a life away from the elder Khelben . Relative time . The year 1371 DR appears to be equivalent to 591 in the Common Year timeline used in parts of Oerth , assuming the Forgotten Realms adventure " For Duty & Deity " and the " Planescape " adventure " Tales From the Infinite Staircase " ( which were marketed as crossover adventures ) both took place in late 1370 DR , and assuming that the adventure " Die Vecna Die ! " ( which included scenes in the " Greyhawk " , " Ravenloft " , and " Planescape " settings ) took place a few months after " Tales From the Infinite Staircase " and " Faction War " , which seems evident from the political situation in Sigil . This is supported by the " Wizards Three " series in " Dragon " Magazine . In " Dragon " # 185 , it ' s stated that the events of the novel " The Parched Sea " , which takes place on Toril , have just recently occured . " Novel Ideas " in " Dragon " # 196 places " The Parched Sea " in 1360 DR . " Dragon " # 185 also places the meeting described in that article prior to the events of the adventure " Vecna Lives " ( which happened in 581 CY according to the Greyhawk supplement " The Adventure Begins " ) , which suggests that 1360 DR equals 580 CY . Spelljammer . In the Spelljammer setting , Realmspace is part of a celestial configuration known as the Triad , which also includes Greyspace , where the world of Oerth is found , and Krynnspace , home of the world of Krynn and the " Dragonlance " campaign setting . The Phlogiston , a rainbow - colored chaotic liquid that surrounds the spheres , has a strong current that flows from Realmspace directly toward Greyspace , making travel in that direction relatively simple ; due to this current , it is impossible to travel directly to Krynnspace from Realmspace . From Greyspace , however , it is a relatively simple matter to travel to either Realmspace or Krynnspace , strong currents leading to both spheres . From Krynnspace one can easily move to Realmspace , but travel directly to Greyspace from Krynnspace is impossible .