Coo is a mechanical bird in the novel The Infernal City.
The small mechanical bird was given to Annaïg Hoïnart by her mother. Coo acts as a magical talisman, in which Annaïg contacts Attrebus Mede with. Coo is also used to save Mere-Glim from being taken to Leyawiin by her father, Taig Hoïnart.
It is most likely Coo is a Dwemer creation, and one of the many active automatons from the days when the Dwemer were alive.