Early medieval (6th century)
Feast: June 9
An Irish prince who started a war over a borrowed book, then spent the rest of his life trying to save as many souls as had died in the battle.
The story goes that Columba secretly copied a psalter belonging to another monk. When the dispute reached the High King, the ruling was blunt: 'To every cow belongs her calf; to every book its copy.' Columba refused to hand it over. The argument escalated into the Battle of Cooldrevny in 561, where three thousand men died. His confessor gave him a penance that would define his life: leave Ireland and win for Christ as many souls as had fallen in the fighting. He sailed to Iona, a tiny wind-battered island off the Scottish coast, and never looked back. From that bare rock he built a monastery that became the spiritual engine of northern Britain. His monks copied manuscripts, evangelized Pictish kings, and planted communities across Scotland. Columba himself was no gentle recluse — he was tall, loud-voiced, politically savvy, and reportedly could be terrifying when angry. But Adomnan's biography also shows him blessing horses, weeping over his monks' hardships, and spending his last hours copying Psalm 34: 'Those who seek the Lord lack no good thing.' He died at the altar on Iona in 597. The island is still a place of pilgrimage.