Beyond the Veil

To gain access to the Otherworld, travelers have to pass through the veil of everyday reality into the strange beyond. Sometimes this veil is a mist or portal at the entrance to a cave; sometimes it is the surface of the ocean, beneath which lies a wonderful land. This theme of things being other than they appear runs through the Otherworld like a seam of silver in a rock-face. Illusions are everywhere, and present a major hazard. Sometimes the supernatural world triumphs, the illusions turn out to be snares, and travelers do not return; sometimes they return safely, even bringing back a precious object with magic properties.

--Juliette Wood, The Celtic Book of Living and Dying