It was with the expectation that he might, with local aid, seize the castle, that Llewellyn invaded this district in December 1282, when he was surprised and killed by Stephen de Frankton in a ravine called Cwm Llewellyn on the left bank of the Irfon, 22 m.
It is situated in the midst of wild mountain scenery on the river Irfon, a right-bank tributary of the Wye.
The Irfon is celebrated as a trout-stream.
Four miles lower down the Irfon valley, at the junction of the Cammarch and Irfon, and with a station on the London & North Western railway, is the village of Llangammarch, noted for its barium springs.
The hilly country to the north of the Eppynt is mainly drained by the Irfon, which falls into the Wye near Builth.
The Irfon valley, near Builth, was, however, the scene of the last struggle between the English and Llewelyn, who in 1282 fell in a petty skirmish in that district.