The Thirteen was a Blackbeak coven under the command of Manon Blackbeak. They were considered to be the fiercest and most disciplined of all the Ironteeth Witches. The Thirteen yielded themselves to destroy the witch tower in Kingdom of Ash.

'For hours Manon knelt on the battlefield, Abraxos beside her. As if she could stay with them, her Thirteen, for a little while longer'

'You won't find them in this sky, or any other', 'I miss them' - Manon to Dorian in the aftermath of the war (about the Thirteen)