Seisyll Bryffwrch was a Welsh language

Welsh language

Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

 poet.

Seisyll competed against and was defeated by Cynddelw

Cynddelw Brydydd Mawr

Cynddelw Brydydd Mawr , in English also known as Kendall, was the court poet of Madog ap Maredudd, Owain Gwynedd , and Dafydd ab Owain Gwynedd, and one of the most prominent Welsh poets of the 12th century.Cynddelw began his career as court poet to Madog ap Maredudd, Prince of Powys...

 in a contest for the role of chief court poet to Madog ap Maredudd

Madog ap Maredudd

Madog ap Maredudd was the last Prince of the entire Kingdom of Powys, Wales and for a time held the Fitzalan Lordship of Oswestry.Madog was the son of Maredudd ap Bleddyn and grandson of Bleddyn ap Cynfyn. He followed his father on the throne of Powys in 1132...

, prince of Powys.

Seisyll's own compositions include elegies on the death of Owain Gwynedd and of Iorwerth Drwyndwn grandfather and father respectively of Llywelyn ab Iorwerth. Seisyll also wrote poems in praise of the campaigns of the Lord Rhys

Rhys ap Gruffydd

Rhys ap Gruffydd or ap Gruffudd was the ruler of the kingdom of Deheubarth in south Wales. He is commonly known as The Lord Rhys, in Welsh Yr Arglwydd Rhys, but this title may not have been used in his lifetime...

.