Trillo was a sixth-century monk of noble birth who originated from Brittany. As a son of Ithel Hael, he traveled to Wales alongside his brothers, Tegai and Twrog. While in Wales, he studied under Saint Cadfan, who eventually welcomed him into the religious life. He rose to the position of Abbot and became recognized for his holiness. He is remembered as the founder of several religious sites and was eventually laid to rest on Bardsey Island.