Anonymous Notices on St. Patrick
Book of Armagh (TCD MS 52)

Patrick came from the plain of Airthice to Drammut Cerigi, and to Namnu Toisciart, to Ailich Esrachtae; and had with him eight or nine men, with tablets in their hands, written after the Mosaic manner; whom the Gentiles seeing, exclaimed that, as they had swords in their hands, they would slay the holy men. Wooden weapons were seen with them, but we think the swords were iron. The multitude desired greatly to abuse the holy men, and to shed their blood ; but there was a merciful man among them, named Hercaith, of the family of Nathus, the father of Feredachus; he believed the God of Patrick, and Patrick baptized him, and hig son Feredachus. And he offered his son to Patrick, and he departed with Patrick for instruction for thirty years, who ordained him in the city of Rome; and gave him the new name of Sachellus, and wrote for him a book of Psalms, which I saw, and he procured for him a portion of the reliques of Peter and Paul, Lawrence and Stephen, which are preserved in Machi.

Cartiacus and Sachellus, the clergymen, having ordained bishops and deacons of the church, without the knowledge or authority of Patrick, in the plain of Asus, he cursed them ; and sending letters to them, they were brought to Armagh, to Patrick, and there did penance. And he told them that they were not of the great and true church.

SOURCE
Betham, William. Irish Antiquarian Researches. Vol. 2. Dublin: William Curry, Jun. and Co., 1827. p 345-346