NIGHTBRINGER | The Arthurian Encyclopedia

Aethlem


A hound needed by Culhwch, as one of his tasks, to hunt the boar Twrch Trwyth. Other tasks required that Culhwch find certain people to manage Aethlem. Arthur obtained the dog for his kinsman.

After the hunt, Aethlem could not be found and was never seen again.


Source
Culhwch and Olwen | Late 11th century