In Déor's reign from 2644 to 2718, the trouble began to return. The Dunlendings began to creep into the territory of the Mark once more and in particular they gained the Ring of Isen and they became too strong for the forces of Rohan to push them out.
References: Unfinished Tales, Lord of the Rings,
Tolkien Quiz Book
Deor, son of Goldwine,
was succeeded by Gram.