Teyrnon Twryf Lliant was the lord of Gwent (formerly in the territory of the Silures tribe in South East Wales). He was also a knight of King Arthur.
After the marriage of Pwyll and Rhiannon, it seemed that Rhiannon was barren and there would be no heir. Pwyll’s advisors suggested he take a second wife. A date was set, but then Rhiannon became pregnant and later gave birth to a son. Following his birth, her son mysteriously disappeared. Frightened of the consequences Rhiannon’s six ladies-in-waiting framed Rhiannon of infanticide and eating her first born by smearing dog’s blood over her whilst she slept.
When news of what happened got out, Pwyll’s advisors told him to divorce Rhiannon. However, now he knew Rhiannon was not barren and could produce an heir, Pwyll did not want to divorce her, but left her punishment to be decided by the courts. She was made to sit outside the city's gates and tell everyone her story for seven years. For eating her child she had to offer to carry all visitors to the city on her back.
In Gwent, Teyrnon, owned a mare whose foals kept disappearing after their birth. One night, whilst guarding his stables, Teyrnon saw a mysterious clawed beast that came to take the foal. Teyrnon raised his sword and severs the arm from the beast. After the beast fled, he discovered a young boy outside the stable. He took the child in and with his wife raised him. He named the boy Gwri Wallt Euryn, meaning Gwri of the Golden hair.
The boy grew up at a faster pace than normal. As he matured, Teyrnon realised the true identity of Gwri. His likeness to Pwyll was unmistakable. Teyrnon took Gwri and reunited him Pwyll and Rhiannon, who renamed him Pryderi. They placed him in the care of Pendaran Dyfed who brought him up carefully, in readiness for the day he would take his father’s place on the throne.
Pwyll was so grateful to Teyrnon that he promised to maintain him and his lands until the day he died. Although offered many fine treasures, the future noble knight of King Arthur respectfully refused them.