Assicus (T'Assach) (d. c.508), an artisan – i.e. coppersmith – of supposed Gaulish origin, came to Ireland at some stage during the mission of St Patrick (qv) and was later consecrated a bishop by him. According to tradition, he was the brother or nephew of Bite, likewise an artisan, who, along with one Essa, are named in the Tripartite Life of Patrick as the three fabri aerarii who attended Patrick. Tírechán (qv), in his ‘Collectanea’ on Patrick, relates: ‘Assicus the holy bishop was a coppersmith [in the service] of Patrick, and he made altar-plates and square casks for the patens of our saint in honour of Bishop Patrick, and three of these square patens I have seen, that is, a paten in Patrick's church at Armagh and another in the church of Ail Find [Assicus's own episcopal church] and a third in the great church of Seól on the altar of the holy bishop Felartus’ (§22, 140–41). A number of his artifacts apparently survived into the later middle ages, if the Tripartite Life is to be believed.
Patrick consecrated Assicus first bishop of Ail Find (Elphin, Co. Roscommon). Several sources, including Tírechán, refer to the tradition that Assicus gave the last rites to Patrick at Saball Pátraic (Saul, Co. Down). Nearby, at Ráith Colptha (Raholp), there are a number of churches and other stone remains associated with Assicus. Later, he fled northwards to ‘Rochuil’ (Rathlin O'Birne Island, Co. Donegal), where he remained for seven years in isolation and solitude because of a lie told by him – according to Tírechán, the lie was told about him. Eventually, his monks came looking for him and took him with them to Ráith Cungai (Racoon, Ballymagroarty Scotch, Co. Donegal), where he later died; his relics were retained there for some centuries (Tírechán, 22.3). His church at Ráith Cungai was later claimed by the Columban paruchia. In the list in the Book of Leinster of the earliest Irish bishops from Patrick onwards his name comes after that of Benignus (qv) (d. 467/8), the last of Patrick's adjutant bishops to die, and before Brón (d. c.511). It is likely therefore that Assicus died in the latter decades of the fifth century or the first decade of the sixth. Rathlin O'Birne, where he remained as a hermit for a number of years, also became an ecclesiastical centre and hermitage. A number of ancient incised stone slabs and crosses survive there, some of which may conceivably date back to the late fifth century. The Martyrology of Óengus (qv) (fl. c.830) gives his feast-day as 14 April; it also records the tradition of his having administered the last rites to Patrick.