Enter at your peril

Leading to Cwm Cerwyn, where King Arthur battled Twrch Trwyth

Gate of Ivory
(originally Gate of Ivory, Gate of Horn)
by Robert Holdstock.
Voyager, 1998 (1997).

At the heart of this fantasy is the medieval Welsh Arthurian tale of Culhwch and Olwen, but there are also echoes of other Celtic texts including The Spoils of Annwn, motifs from classical mythology and references to more recent fiction such as Bunyan’s Pilgrim’s Progress.

Christian Huxley, like his father before him, ventures into an ancient woodland — Ryhope Wood — peopled by figures from myth and legend and emanations from dreams and imaginations, following a personal quest born in tragic circumstances.