Thalis is the High Protector of the Order of Avacyn. She is a high ranking member who works closely with the Mikaeus who is highly revered in Gavony. Thalia runs the Order side of Church of Avacyn which means she is in charge of the inquisitors and the fighting side of the order.
The party met her and helped her end the necromancers Gisa Cecani and Geralf Cecani.