A late legend, based on a naive reading of the toponym Cantium, says he was born in Canterbury,[1] and served as an imperial dignitary before becoming a bishop.
He is credited with building the original Basilica of Sant'Abbondio outside of the city walls of Como.
The basilica was built to house several relics associated with Peter and Paul, which Amantius had brought from Rome.
[1] His relics were preserved at Sant'Abbondio until July 2, 1590, when they were transferred to the Chiesa del Gesù in Como.
The relics were later transferred to the church of San Fedele in Como, where they remain today.