Unless stated otherwise, all information herein is taken from A Memory of Light, Prologue.
Dennel is a a captain in the Band of the Red Hand who is in charge of the Dragons. He was involved the the defence of Caemlyn. He brings Talmanes a map and tells him of a way through the city and later helps him in a fight against a Trolloc. When Talmanes reminds him that the Dragons can level an enemy bulwark in just a few shots, he immediately realises they can break one of the city walls and allow them to escape.