Planet believed to have once been home to the "Holy Grail" -- the Sangraal, part of the Ancient Merlin's powerful anti-Ori weapon. SG-1 found the address to the planet by combining symbols from the addresses to Castiana, Sahal, and Vagonbrei -- three planets at equal distance from the Camelot planet. (Together the coordinates of the four worlds form a perfect tetrahedron.)
Morgan Le Fay made certain that this planet was only accessible via Stargate, as Goa'uld and Ori warships alike could not reach it from space. While SG-1 did not find the Sangraal itself here, they did find the path forward to locating Merlin himself by means of entrance to Morgan's planetary circuit.
Today the world is home to a pre-industrial settlement of humans, including Osric, who guide those in search of the Sangraal in the appropriate direction. The people were eventually besieged by the Ori, who had come on foot to destroy the Sangraal. Like many countless worlds in the Milky Way Galaxy, its inhabitants were forced to bow down to the teachings of Origin or face annihilation.
The Quest, Part 1 - SG-1 visits Osric's planet in the hopes of uncovering the Sangraal and halting the Ori's evil pilgrimage once and for all.