As far as can be judged from the few facts which can be extracted from his cywyddau, Siôn Cent wrote his poems between 1400 and 1430. He wrote a eulogy of Brecknock which at least proves that he was well acquainted with that part of Wales and that he had a liking for it. But the rest of the work attributed to him — much of it, there is little doubt, incorrectly — consists of religious cywyddau. His subjects are confined to the uncertainty of life and all that pertains to it, and to the inevitability of death and the last judgement. When Rhys Goch Eryri and Llywelyn ap y Moel (qq.v.) were engaged in a discussion as to the origin of the muse and agreed that it was derived from the Holy Ghost, Siôn Cent intervened and asserted that the muse of the Welsh bards was a lying muse. Unfortunately, all that remains of this dispute is one cywydd by Siôn Cent and one by Rhys Goch in reply to him. It is reasonably certain that at least one of Siôn Cent's cywyddau has been lost. He sang of life and the world as he found them — pessimistically, for the most part, although he brightened up when he mentioned heaven. His cywyddau have one unusual feature, namely that they are divided into stanzas, the last line of each being the same and acting as the burden of the poem.