A spurious tale was later recorded that the abbey was founded in 1143 by Meredudd ap Maelgwn at Ty-faenor, and then refounded at the present location near the village of Abbeycwmhir in 1176.
The original lord of Maelienydd, a Welsh prince, Cadwallon ap Madog, was killed by the English Sir Roger Mortimer of Wigmore on 22 September 1179.
The headless body of Llywelyn ap Gruffudd, last native Prince of Wales by direct descent, was buried in the abbey after his death in battle nearby in December 1282.
In the early 13th century, the construction of what would have been a spectacular and spacious abbey church were embarked upon, equal in scale to many a cathedral probably by Llywelyn ab Iorwerth.
The ongoing political and social troubles were undoubtedly the cause and the abbey fortunes diminished even further during the significant damage inflicted during the uprising of Owain Glyndŵr from 1401.