Wikipedia
Penpingion
Penpingion is one of the gatekeepers at Arthur's court in early Welsh Arthurian traditions in which he is subservient to Glewlwyd Gafaelfawr. He appears in two tales: Culhwch ac Olwen and Geraint fab Erbin, and is described as having supernatural abilities: he "goes about on his head to save his feet, neither looking to heaven nor to the ground, but like a rolling stone on a court floor".
He takes part in the hunt for the Twrch Trwyth and is killed in the attempt.