Tydfil the Witch

Tydfil is a cowalker faerie witch that was originally the reflection of the Cambrian martyr Saint Tydfil of Brycheiniog, a beloved princess and benevolent religious leader who was slain by Pagan raiders while praying in 480. The witch is trapped in Merthyr Tydfil, the village named after the princess. Ever since the princesses death, the witch has grown uglier and less human, taking on the appearance of an old hag.
Tydfil is the witch that Sir Pelledak of Lighthorne trades his daughters Lady Favour of Huntington and Lady Orcade of Lighthorne to in exchange for a male heir, Sir Artaire of Idmiston, who was fashioned out of clay. As the transaction was never completed, she placed a curse on Sir Pelledak so his children cannot bear heirs.
She appears to have some connection with the redcap Eeder-Foalley-Jollyssagh.
After lifting the curse on Sir Pelledak's kin, she is currently loose in the world.