Dunster Castle motte, or Upper Ward, and an area below shaped to form the bailey, or Lower Ward. Somerset became more stable in the aftermath of the post-invasion period and the unsuccessful 1068 rebellion against Norman rule. It was common in the period for the Normans to build religious houses to accompany major castles, and accordingly William de Mohun endowed a Benedictine priory at Dunster in 1090, along with its parent abbey at Bath. The River Avill was important for trade; the region around Dunster was rich with fisheries and vineyards, and Dunster Castle prospered. Stone fortifications were built on the site
Yarn Market, Dunster on the motte by the start of the 12th century, and the castle survived a siege during the early years of the Anarchy. At the end of the 14th century the de Mohuns sold the castle to the Luttrell family. Dunster had become a centre for woollen and clothing production by the 13th century, with the market dating back to at least 1222, and a particular kind of kersey or broadcloth became known as 'Dunsters'. The prosperity of Dunster was based on the wool trade, with profits helping to pay for the construction of the tower of the Priory Church