Complex sentence: Glywys (;) is a legendary early 5th century Welsh king, an important character in early Welsh genealogies as the eponymous founder king of Glywysing, "The Welsh Academy Encyclopaedia of Wales".
Split into simpler sentences: Glywys (;) is described in Welsh genealogies as an early 5th century Welsh king who is seen as an important character in early Welsh history. The kingdom of Glywysing is believed to have been named after Glywys, "The Welsh Academy Encyclopaedia of Wales".