The Book of Sky is a magical book of spells dealing with the healing of the mind. The Book was kept in the Brigobaen library until the Book of the Stars was recovered, prompting a Temple Priest to hand a cleric named Varto the Book of Sky, who gave it to the cleric Dharma. The Book of Sky cannot be used without the Amulet of Sky.
During the Red Moon of 438, a large group of clerics, instructed by Nafets, made their way to the Temple on the seas of Skull Island in order to make the first known attempt to use a spell from the book. The aim was to help Beleth recovering his wizard skills. The clerics gathered around the Royal Mage singing from the book the words *pur clar resti'niul *. In the centre, Beleth was wearing the matching amulet, that he had found in a hidden level of the Tower of Nystral a few days before. Eventually, the spell worked as desired. As they were chanting, hordes of Bone Mages attacked the healers. It is unknown if that occurrence was a side effect of the ritual.