The Father is a 4th level cleric, and will sell his services for anything that is not blatantly evil.
He has 3 potions of greater healing for sale for 150 gold each. If his magic is exhausted one of the other priests will take his place.
Father Cartick is a priest of Mithras from the Cathedral of Mithras the Risen.
He has a small stall in the The Pirate Market where he dispenses cures and lifts curses. He also has a small stock of healing potions.