The church in Subulter was built in around 780. It was built in a Romanesque style with local limestone. The church was at the centre of an old Gaelic settlement called Mona na Mandaragh. The settlement was probably built by followers of St Berrahert of Tullylease. St Berrahert is credited with converting a druidic settlement (which was probably located around the present site of Marybrook House).
An effigy of Síle Ní Gig, the supreme druidic Goddess of fertility, was set into the wall of the church in Subulter when it was built and later transferred to the Holy Well in Castlemagner. This suggests a strong converted druidic association with the early Christian church in Ireland. This would be in keeping with the Celtic Christian practice and teaching of this time.
The church was in continuous use until 1461. Fr Domatus Morrisey was the last priest to serve there. The land around the church was used as a burial ground by local families up to 1900 and for 40 years after for the burial of unbaptised infants. All that remains today is a section of a side wall of the church and about 1 acre of burial ground. The church is situated in what is known locally as the ‘Church Field’.