Stag of Rhedefre, Stag of Rhedenfre
The Stag of Rhedefre was the second “wise animal” that Arthur’s warriors encountered on their quest to find the imprisoned warrior Mabon.
Having been directed to this animal by the Blackbird of Cilgwri, the party helping Culhwch in his search for Olwen were passed on to the Owl of Cwn Cawlwyd, which, in turn, took them to the Eagle of Gwernabwy, which finally took them to the Salmon of Llyn Llw.
See also
White Stag | The Legend of King Arthur
Source
Culhwch and Olwen | Late 11th century