The three great Nights of the Spirits (Ysbrydnos ) when the boundaries were blurred between physical world and spirit world, the spirits roamed the earth. The Brythonic folk festivals and wheel of the year in relation to their Gaelic counterparts. Nos Calan Gaeaf (Samhain), Gŵyl Fair y Canhwyllau (Imbolc), Nos Calan Mai (Beltane) and Calan Awst (Lughnasadh).