It is said he joined with Urien of Rheged and Morcant Bulc in their ill-fated alliance: Four kings fought against them, Urien and Rhydderch and Gwallawg and Morcant.
Dise que entrou con Urien de Rheged e Morcant Bulc na súa malfadada alianza: Catro reis loitaron contra eles, Urien e Rhydderch e Gwallawg e Morcant.