A moratorium is in effect on adding information from Fire and Blood until December 20th.
A Clash of Kings (mentioned)|
A Storm of Swords (mentioned)
A Feast for Crows (mentioned)
A Dance with Dragons (mentioned)
A Clash of Kings
Dunsen is one of Ser Gregor Clegane's men at arms and is part of the group that captures Arya Stark, Gendry and Hot Pie in the Riverlands. He took Gendry's bull helm. For this, Arya adds him to her prayer kill list.
Dunsen later departs Harrenhal alongside Tywin Lannister as part of Gregor Clegane's vanguard, unknowingly putting himself out of Arya's reach to choose him as her next target for Jaqen H'ghar. Polliver is seen wearing Gendry's bull helm as the standard bearer of Ser Gregor when leaving, supposedly having taken it from Dunsen..
Dunsen participates in the Battle of the Fords under Ser Gregor Clegane's command, managing to cross the trident as one of his best men. He survives the battle at Stone Mill and successfully retreats when Ser Edmure Tully counter-attacks with his reserve.
A Storm of Swords
Dunsen continues to be religiously included in Arya's death prayer list, though as time goes on she struggles to remember his face as well as the other marked members of Ser Gregor's men-at-arms.
A Feast for Crows
Dunsen remains stationed at Harrenhal with the remnants of Ser Gregor Clegane's men at arms. After the fall of Riverrun, Dunsen's group, led by Raff the Sweetling, was told to escort Ser Robin Ryger and Ser Desmond Grell to Maidenpool for their journey to the Wall to make sure they made it there alive.