Motivated by love for his flock, the holy bishop of Euroea killed a dragon by striking it with a riding whip, thereby delivering villagers from the beast. At the same time, he sweetened the waters of a spring that had been poisoned by the dragon by his God-pleasing prayers. Having received word of these miracles, the Emperor Theodosius the Great and his wife entreated the saint to pray for their daughter who was being tormented by a demon. Saint Donatus rebuked the demon, and it immediately fled leaving the girl in peace. When offered a reward out of gratitude, the saint refused it asking instead for the sovereign to build a new church in his diocese. For these and other such things, Saint Donatus was venerated as the protector of Epirus.