Theoradus was the dragon that lived in a cave near Creel's home, Carlieff. He kept a hoard of shoes (Human shoes) and he gave Creel a pair of shoes from his hoard, and those shoes turned out to be the "Dragon Slippers" of which the book is named.
Theoradus was a brown male dragon with a rack of golden horns.
Before, Theoradus used to kidnap princesses and let knights or princes to fight him. Later, he got tired of all these (he stopped since Creel's grandfather's time).
When Creel was sent to him as a sacrifice he came out and ushered her inside. He revealed that he's exhausted of humans and wants nothing to do with her or her 'prince'. Theoradus also told Creel that dragons do not collect golds but different types of things, example him collecting shoes (Human shoes). Creel traded him his solitude for a pair of shoes from his hoards. She then picked a pair of beautiful azure blue slippers 'The Dragonskin slippers', much to his dismay and off her way to King's Seat.
Theoradus later passed away in the First Dragon War. Creel's brother Hagen was given the honor to be the curator of Theoradus' Museum. In another words, Theoradus' hoard of shoes were displayed to the public for humans and draconic.