The Great Welkynd Stones were the pinnacle of Ayleid magical stones. They are large pieces of meteoric glass that were cut and enchanted by the Ayleids.
The only known existing stone is the stone of Miscarcand, which the Hero must retrieve in the main quest, the Miscarcand quest. For more information on Welkynd stones in general, read the book Magic from the Sky.
Inside the ancient Ayleid ruins of Miscarcand, the Hero will find the Great Welkynd Stone, required to open the gate to Mankar Camoran's Paradise. No one has ever managed to obtain this Great Welkynd Stone and it is rumored that the undead King of Miscarcand guards the Great Welkynd Stone himself.