A member of the Sidhe Ardaithe. According to Grifo Bunce, she broke their law by amassing too much magical power and potentially threatening the balance of their society, and was imprisoned with him in Uaigneach.
She broke out of Uaigneach by possessing Yegu, an elven fighter whose band of ruin scavengers was exploring its echo in the material plane. She appears to want to head towards civilization, and retails some of her ability to planeswalk.
Rionach was killed at Briste, and stored in the party's bag of holding.