Summer requests begin with Rhiannon, the Welsh Otherworldly figure, perhaps a goddess, from the Mabinogion. She is associated with horses, and is similar to Celtic figures like Morrigan and Medb with her connection to sovereignty. We look at the significance of her story from the first and third branches of the Mabinogi, with a discussion of horses as chthonic symbols, and the idea of initiation with respect to the Otherworld.