Surviving documents testify to Domentius' efforts to aggrandize the church's land properties and restore those holdings that had earlier been lost to secular noble landlords.
According to the early-18th-century royal historian Prince Vakhushti, Domentius "was installed" as catholicos by King Simon I immediately after his accession to the throne of Kartli in eastern Georgia in 1556.
Domentius' rule was limited to the eastern Georgian territories, with his see at Mtskheta; the west was under the jurisdiction of the breakaway Catholicate of Abkhazia.
Even in the east, the Kingdom of Kakheti, run by a dynasty vying with their royal cousins in Kartli, tried to establish its own church.
Further, in 1560, George, Crown Prince of Kakheti, restored to the see of Mtskheta a number of estates earlier lost by the church to that kingdom.