Answer
In 1216, Llywelyn gained princely power in Powys Wenwynwyn, a territory in modern-day Wales, in addition to his power in Gwynedd. This expansion of his power was due in part to the death of King John, who had been supporting the lord of Powys Wenwynwyn, Gwenwynwyn. Llywelyn took advantage of the situation to seize control of the territory.