Yoren is a member of the Night’s Watch whose role is to travel Westeros seeking recruits for the Night’s Watch.
He was in King’s Landing on the day that Ned Stark was executed. Ned managed to indicate to Yoren that his daughter Arya was standing on Baelor’s statue. Yoren reached Arya just before Ned was executed and prevented her from witnessing the act.
Yoren disguised Arya as a boy, ‘Arry, in order to take her north to her family. Also in the party was Gendry, the bastard son of Robert Baratheon. They were set upon by a group of gold cloaks looking for Gendry but Yoren managed to see them off.
When a group of Lannister men, led by Armory Lorch, demand that Yoren gives up Gendry, another fight breaks out. This time Yoren was not able to see them off and was killed.