He initially began to train as a Columban priest,[1] but left to study English at University College Dublin and then joined a graphics company as a screenwriter.

He was in the pioneering Irish Celtic rock band Horslips as bass player, vocalist and front man.

[4] He co-wrote with Paul J. Bolger Hound, a graphic novel trilogy based on the Ulster Cycle that got limited release from 2014 to 2018 before Dark Horse published an omnibus edition.

[5][6][7][8] In 2015, Devlin won the Best Writer Published in Ireland award at the Irish Comic News alongside Paul for Hound.

[9] His sister, Marie Devlin, is a school teacher and writer, who published Over Nine Waves, a collection of traditional Irish myths and legends, in 1994.