" The Tylwyth Teg were immortal beings, but the burden of living for endless millennia was often tedium. It was one reason that the Fair Ones tended to play terrible pranks upon mortals. Like bored children, they sprang upon the unwary, seeking diversion. So it had been when a weary Celtic warrior turned reluctant gladiator had fought his way to freedom at last. Wounded and near death, pursued by his former captors, he’d blundered straight into the territory of the Tylwyth Teg in the steep hills northwest of Isca Silurum…. "

― Dani Harper , Storm Warrior (Grim, #1)