Kaw first appeared to the Companions in a Fair Folk waypost in the Forest of Idris, near to Annuvin. Princess Eilonwy was the first to spot him; Fflewddur Fflam remarked on the cleverness of his name. Kaw mischievously revealed the names of the three enchantresses of Morva, spurring the companions on their quest to find the Black Crochan. After the Cauldron had been destroyed, Gwystyl gave Kaw to Taran, explaining "that's what he wants", and admonishing Taran never to listen to a word Kaw said.
Kaw retrieved the finger-bone that was key to defeating the wizard Morda, even after Taran had returned the sliver to its resting place, believing it was either worthless or dangerous. The bone proved to be a phylactery in which the wizard had placed his life-force, and which protected Taran from Morda's spells.
Kaw first alerted Taran and Gurgi to the return of Eilonwy to Caer Dallben. Later, at Taran's command, Kaw flew to Annuvin to scout the way for Prince Gwydion. Still later he flew to the valley of Medwyn, who after the crow's warning, summoned the wolves Brynach and Briavael to attack the Huntsmen of Annuvin.
Kaw returned to the Realm of the Fair Folk at the conclusion to the series. Given his origins, his preternatural intelligence and his comprehension of dire matters, it's possible Kaw had some measure of Fair Folk enchantment.