St Erfyl was a virgin from whom the church of Llanerfyl in Powys arose. There is a Romano-British stone now kept inside the church with an inscription commemorating a young 13 year old girl called Rustica. This has mistakenly been believed to be her grave stone. However some fragments of wood are said to be part of St Erfyl’s shrine and reliquary. 400 yards west of the church are the remains of an ancient yew tree and a holy well beneath it.
In the large church at Meifod nearby in Powys is an impressive grave slab with two crosses, one eastern and one western one above the other. Decorated with Welsh and Viking motifs and dated to 9C the stone may have once covered the coffin of a prince of Powys. The church is said to have been founded in the 6C by St Gyddfarch. It was here that St Tysilio gave himself to the monastic life. The monastery became a large one.