A Gifted scion of the wealthy Ua Gallchobhair clan in Ulster, and one of the founders of Feirm Fedelm.  A Mentem specialist, though he is less focused on magical research or feats these days, and more focused on writing poetry and histories, and regaling everyone around him with these.  He is indeed a talented storyteller, equally proficient in both Latin and Gaelic, and not bad in English or Norman French either.

Tiarnach appears to be in his early 50s.  He has a round face and short, dark brown hair.  He dresses according to the fashions of Irish nobility, and seems to take more care than other magi in ensuring that his clothes are clean and neat.