Complex sentence: Colman was stepping into a landscape that had been decimated by the plague of 664-665, and may have been reviving an earlier church on the island, or indeed one in the area in central Connacht where Mag Éo was founded later.
Split into simpler sentences: Colman was stepping into a landscape that had been decimated by the plague of 664-665. He may have been reviving an earlier church on the island or one in the area in central Connacht where Mag Éo was founded later.