Background and education
The sources agree that Leontios came from a prominent family of Monemvasia and was baptized Leon. The OCA life describes his parents as Andrew and Theodora and records that he studied foreign languages, philosophy, and theology at Constantinople, after which he was appointed to an important position in the central administration of the Morea (the Peloponnese).
A later tradition, reflected in Wikipedia and Greek accounts, elaborates his lineage, naming his mother Theodora as a daughter of the emperor Andronikos II Palaiologos and his father Andrew as governor of the Peloponnese. These dynastic details are not uniformly attested and are reported here as tradition.
Monastic life and ministry
After his father's death Leontios returned to care for his mother; once she withdrew to a monastery he married and, by the OCA account, was a model husband and head of his household. The death of his wife and children turned him to the monastic life, in which he received the name Leontios.
He is said to have trained under an experienced ascetic named Menides and to have spent time on Mount Athos before returning to the Peloponnese. He then settled on a mountain near Aigialeia, in the region of Achaia, where he lived as a hermit and preached the faith through the cities of Achaia, influencing many who entered the clergy.
Repose, monastery, and relics
Leontios reposed peacefully. At the site of his ascetic struggle a monastery of the Archangels arose; the sources differ on the founders, the OCA life naming the brothers Thomas and Anthony Palaiologos and Greek accounts naming his uncles Thomas and Demetrios Palaiologos as patrons of the foundation, which is identified with the Monastery of the Taxiarchs (Pammegiston Taxiarchon) near Aigio.
His relics are kept in a shrine in the church of the Holy Archangels within the monastery at Aigialeia. While the anchor record places him in the post-Byzantine, fourteenth-century context, some external sources date his birth to 1377 and his repose to 1452; these dates are reported by those sources but are not certain.