Reaper

Reaper is Agatha's cat, In the first book Reaper was her pet, But in the 2nd book, Reaper turns against Agatha. He becomes a lot less friendly with her, but still never maims her. Reaper was found by Callis in the Endless Woods, abandoned by his parents because of his hairless shape. Callis brought him back to Gavaldon to escape the School Master.

Reaper (In the Endless Woods)
Reaper is known as 'C.R King Teapea' to the gnomes of Gnome land. Agatha, Sophie, Tedros, and their friends turn to King Teapea for help, not knowing that the king was Agatha's cat. Teapea helps them try to stop Rhian from becoming "The One True King."