He was born in the 5th century at Lichos, in the lower valley of the River Saison, into a Catholic family.
Euric's successor, Alaric II (485-507), was tolerant towards them, permitting among other things the creation of Catholic bishoprics, including that of Oloron, of which Gratus was the first bishop.
He took part in the Council of Agde in 506,[1] where 34 Catholic bishops of the Visigothic kingdom met under the chairmanship of Saint Caesarius of Arles.
Gratus is believed to have died at Jaca during this period, from where his body was retrieved and brought to its place of permanent rest in Oloron-Sainte-Marie.
The Cathedral of Oloron-Sainte-Marie was decorated with five gilt and polychrome wooden panels depicting the scenes from the earth and heaven life of Saint Gratus