In 915, the area faced an incursion from Vikings led by Ohter and Rhoald, coming from the River Severn. After first capturing Cyfeiliog (Cimeliauc), the Bishop of Llandaff, they were defeated in battle by the combined forces of Gloucester and Hereford, possibly at "Kill Dane Field" near Weston under Penyard.
Archenfield, which lay beyond Offa's Dyke and outside the Hundred system, became a semi-autonomous Welsh district, or commote, with its own customs. Its administrative centre was at Kilpeck Castle. Its customs were described in a separate section of the Domesday Book account of Herefordshire. Domesday recorded that "King Gruffydd and Bleddyn laid this land waste before 1066; therefore what it was like at that time is not known". It also stated the Welsh of Archenfield were allowed to retain their old rights and privileges in return for forming an advance and rear guard when the King's army entered or left Wales. The local priests were required to "undertake the king's embassies into Wales", presumably providing a translation service. The exemption from services was mentioned again in 1250 and 1326, when it was stated: "The Frenchmen and Welshmen of Urchenesfeld hold their tenements in chief of our lord the King by socage, rendering 19 pounds 7 shillings and 6 pence. And they ought to find 49 foot-soldiers for our lord the King in Wales for 15 days at their own cost."
Uncertainty over the border persisted until the Laws in Wales Acts of 1535 and 1542, often known as "The Acts of Union", tidied up many of the administrative anomalies within Wales and the Marcher borderlands. However no consideration was given at the time to ethnic or linguistic realities, and so various territories were grouped together in a rough and ready manner to form the new shires. Archenfield was thus bundled into Herefordshire, as the Hundred of Wormelow. However, it remained a predominantly Welsh speaking region until at least the 17th century, and the language was still spoken in the Kentchurch area as late as 1750. The evidence of its Welsh history remains in many placenames and field names.
Many of the rights and customs of the people of Archenfield were maintained until comparatively recently. Men born in Archenfield had the right to take salmon from the River Wye until 1911. In King's Caple, the only part of Archenfield east of the Wye, Domesday lists the inhabitants as one Frenchman and five Welshmen. Six local men paid the dues which had been owed at this time, and before, for centuries. Payment was still being made by one of these 'King's Men of Archenfield' in the 1960s.
The symbol of Archenfield and, specifically, of the town of Ross-on-Wye is the hedgehog, known in Middle English, and locally, as an "urchin". It has been speculated that the names "Archenfield" and "Ergyng" may ultimately derive from the Latin word for hedgehog, hericius, from which "urchin" is also derived.