Iolo makes the figure of Geraint, otherwise unattested in Welsh manuscript sources or tradition, the inventor of cynghanedd and brother of king Morgan of Morgannwg. He even went so far as to equate him with Asser in the court of Alfred the Great.
Iolo attributes the creation of cynghanedd and kinship with King Morgan of Morgannwg to a character unnamed in Welsh sources or lore. He also sought to connect this figure to Asser at Alfred the Great's court.