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
Feudal barony of Dunster (1303–1377) and widow of Sir John de Vere, son of the Earl of Oxford. In the following year 1375 Lady Mohun's husband died, being the last in the male line of Mohun. In the following year 1376, Lady Mohun completed the transaction, namely that her trustees settled the castle of Dunster, the manors of Kilton, Minehead and Carhampton, and the hundred of Carhampton on Lady Mohun for her life, with remainder to Elizabeth Luttrell and her heirs. Lady Elizabeth Luttrell never lived at Dunster, as she died in 1395 before Lady Mohun's life interest had expired. But Dunster Castle remained