Dunstan is the solution to the medium anagram clue: Sand Nut. His challenge scroll answer is 8.
Dunstan is featured in several quests: Death Plateau, Troll Stronghold, Troll Romance and Desert Treasure. In Troll Stronghold, his son, Godric, a member of the Burthorpe Imperial Guard, is taken captive by Mountain Trolls and must be rescued. During Troll Romance the player requires Dunstan's help in making a sled which is used to access Trollweiss Mountain. During the Desert Treasure quest, Dunstan requires an iron bar and a pair of climbing boots to make a pair of spiked boots, which are needed to traverse the Ice Path.
Dunstan can repair degradable armours, such as barrows equipment, for the player at a price. The equipment does not need to be fully degraded in order to have it repaired. The cost of any repair is proportional to how degraded the item is. Alternatively, players can repair the armours at a cheaper price themselves at an armour stand in any player-owned house.