The Forbidden Lore pertains to the magic of the Great Dragons in particular their ability to change form and become human. It was considered by the Dragons better not to left humans know they had magic and that they could come and go as they pleased in human society. The first known instance of this knowledge being revealed to humans was when Rhuagh revealed it to Macros after their epic battle. Later it was revealed by Ryath to Pug and Tomas when they along with Macros escaped from the Garden to the Hall of Worlds but only on the condition that they never reveal it to anyone.