Episcopate and the Council of Nicaea
According to tradition, Achilles was distinguished for his holiness of life and his learning before he became bishop of Larissa in Thessaly. He served during the reign of Saint Constantine the Great.
He took part in the First Ecumenical Council, where the assembled fathers addressed the Arian heresy. The synaxarion records that he boldly denounced the heresy, and he became renowned for his vigorous defense of Christian orthodoxy. The OCA troparion (Tone 4) describes him as 'a rule of faith, an image of humility and a teacher of abstinence.'
By tradition, after returning from Nicaea he demolished many pagan temples, built numerous churches, and performed exorcisms throughout his diocese. The 1910 Catholic Encyclopedia noted him as a bishop celebrated for his miracles.
Miracles & Traditions
Traditional Accounts: A miracle recounted in church tradition records that Achilles challenged the Arians at the Council by taking up a stone and calling to them: 'If Christ is a creature of God, as you say, tell oil to flow from this stone.' When the heretics remained silent, he invoked orthodox doctrine, and oil flowed from the stone, astonishing those who witnessed it. He was glorified with the gift of wonders.
Relics & Shrines
Between 977 and 983, after a successful siege of Larissa, Emperor Samuel of Bulgaria obtained the relics of Saint Achilles and had them laid in a church built for that purpose on an island in the Small Prespa Lake (Lake Prespa, Greece). The island is now named Saint Achillius (Agios Achillios) after the saint whose relics were enshrined there.
The Basilica of Agios Achillios on the island later became historically significant: in 1965 the Greek professor Nikolaos Moutsopoulos found Samuel's own grave within the Church of St Achillios, and the ruins of the basilica stand as testimony to Samuel's patronage and architectural legacy.
