Yoren is a sworn brother of the Night's Watch. He suffered a shoulder injury meaning he couldn't fight well, so has spent the next 30 years wandering the Seven Kingdoms as a recruiter, known as a wandering crow. In that time he has only lost 3 recruits. He has a loyalty to House Stark, as his travels would frequently bring him to Winterfell.
Yoren, while transporting two rapists from the Fingers, meets the Watch's First Ranger Benjen Stark, who is returning from visiting his brother Eddard Stark, Lord of Winterfell. Ned's bastard Jon Snow is travelling with his uncle, intending to join the Watch. Tyrion Lannister is also there, wanting to see the Wall.
Yoren then departs south with Tyrion and four black brothers. At the Inn at the Crossroads Catelyn Stark arrests Tyrion, suspecting him of trying to murder her son Bran Stark. Yoren proceeds to King's Landing to inform Eddard of his wife's actions.
While in King's Landing a man (Varys in disguise) gives Yoren gold to take a boy, Gendry (secretly a bastard of King Robert Baratheon) to the Wall. When the Lannisters usurp the throne after Robert's death Eddard is imprisoned for trying to support the rightful King, Robert's brother Stannis Baratheon. Eddard, fearing for his daughters, agrees to 'confess' to treason. Yoren is told to be ready to take him to the Wall. However Joffrey Baratheon has Eddard executed instead. Eddard's younger daughter Arya Stark has escaped the Lannisters and is living on the streets of King's Landing. Yoren finds her in the crowd watching her father's execution and drags her away, calling her "boy". He cuts of her hair, telling her she will pose as an orphan boy called Arry, and he will take her to Winterfell.
Yoren's group consists of about 30 people, most orphans from the street, some from the Black Cells Eddard allowed Yoren to search. 3 of the recruits, Jaqen H'ghar, Rorge and Biter, are kept chained in a cage. Yoren keeps calling Arya "boy", reminding her to keep up her disguise. Round the band are signs of war. Eddard's son Robb Stark has arrived in the Riverlands to fight the Lannisters and been declared King in the North by the Northern Lords and River Lords in response to his father's death, trying to secede from the Iron Throne. Meanwhile Stannis, having found out that Cersei's children were not sired by Robert, has declared himself King. Robert's youngest brother, the vain and ambitious Renly Baratheon, has made alliance with the powerful House Tyrell by marrying the daughter of the arrogant and greedy Mace Tyrell, and plans to usurp the throne himself. The Seven Kingdoms has thus been plunged into war, though Yoren thinks they will be safe as the Night's Watch takes no part in the wars of the realm. One of the recruits, Praed, dies, making him the fourth recruit Yoren has lost.
Goldcloaks are sent after the procession by Joffrey's mother Cersei Lannister due to her purge of Robert's bastards, which could be used to prove her children are illegitimate. Yoren, however, is able to send them off. They approach the lake called the God's Eye, next to Harrenhal. Yoren isn't sure how to cross the lake, and decides to shelter for the night in an abandoned holdfast. However a party led by the Lannister Knight Ser Amory Lorch burns the town and order Yoren to open the gate in the name of King Joffrey. Yoren refuses, saying the Night's Watch takes no part in the wars of the realm. Lorch orders his men to kill everyone in the Holdfast. Yoren organizes the defence of the Holdfast, but on realising the attackers have won he orders "Arry" to take Gendry and as many boys as possible, and flee through the flight tunnel found earlier. That is the last Arya sees of him.
The next day she returns and finds everybody dead. Yoren's skull has been split open by an axe and he is surrounded by the bodies of four enemies. Arya and the boys only bury Yoren, as they don't have time to bury everybody.
Later Harrenhal falls to Roose Bolton, one of Robb Stark's commanders, after the sellsword company the Brave Companions are persuaded to betray the Lannisters. Lorch is thrown into the bear pit by the Brave Companions as entertainment. The big black bear reminds Arya of Yoren, which to her makes Amory's death satisfying.
- In the HBO Show Yoren gives Arya the idea of reciting the names of those she wants dead each night. He tells her his brother was murdered by Willem and each night he'd remember Willem. When they rode back into town Yoren buried an axe so deep in Willem's skull they had to bury him with it. He took Willem's horse to get to the Wall.
- Yoren's death is slightly different in the show. He is hit by a crossbow bolt, but kills the man who fired it. He kills several more men, but is wounded and Lorch delivers the killing blow by driving a sword through the back of his neck.