- "It's the greatest armada Westeros has ever seen. With the Iron Fleet, you own the seas!"
- ―Euron Greyjoy
During the Greyjoy Rebellion, the Iron Fleet led by Lord Euron Greyjoy raids Lannisport, destroying the Lannister fleet. The Iron Fleet was later defeated by the forces of Lord Stannis Baratheon at the Battle of Fair Isle. Following the Siege of Pyke, the Ironborn ruler Balon Greyjoy sues for peace and submits to King Robert Baratheon. His youngest son and heir Theon Greyjoy is sent to live as a ward of Lord Eddard Stark.
At the Kingsmoot held after the death of Balon, Yara vows to build the "mightiest fleet" to conquer the mainland. However, she is outmaneuvered by her uncle Euron, who advocates forging an alliance with Daenerys Targaryen in order to gain access to her dragons. While Euron is being baptized by Aeron Greyjoy, Yara, Theon, and their supporters flee on the best ships in the Iron Fleet. In response, Euron orders his supporters to build another fleet and to kill his niece and nephew.
Yara and Theon's Iron Fleet sails to Essos with the intention of beating Euron to Dany, who lives in Meereen in Slaver's Bay. On the way, they stop for rest and relaxation at the Free City of Volantis. At Meereen, Yara and Theon forge an alliance with Daenerys and her advisor Tyrion Lannister. In return for recognizing the independence of the Iron Islands and helping them to overthrow Euron, Yara agrees to ferry Dany's army to Westeros and to cease raiding the mainland. Later, the Iron Fleet is seen sailing as part of a combined Targaryen armada to invade Westeros.
After Yara and Theon abscond with their best ships, Euron considers his remaining bulk of the Iron Islands' naval forces to be the real "Iron Fleet" and refers to it as such (comparable to how both Joffrey Baratheon and Stannis Baratheon considered their own fleets to be the "Royal Fleet" when they faced each other).After Cersei Lannister declares herself queen, Euron arrives in King's Landing to offer her a marriage-alliance and his Iron Fleet. Given that Cersei has personally alienated the North, Dorne, and the Reach with blood betrayals, Euron is the only major faction left who would be willing to ally with her - and given that Yara's faction sided with Daenerys, who has allied with Cersei's younger brother Tyrion Lannister (who killed their father), Euron claims that this makes Cersei his natural ally. Cersei remains unconvinced of his trustworthiness, given that Euron killed his own brother to seize rule of the Iron Islands. He sees her point, and departs offering that he will return with a great gift to prove his worth.
The Iron Fleet, under Euron's command and having just left King's Landing, attacks a portion of the Targaryen fleet under Yara's command as it leaves Dragonstone heading to Dorne. Euron's ships launch fireballs into Yara's, crippling the Targaryen fleet and giving naval superiority to the Iron Fleet.
The Iron Fleet returns to King's Landing where Euron parades his captives through the streets - to the amusement of the citizens. Euron delivers Ellaria and Tyene to Cersei, fulfilling his promise of a gift by handing her the people responsible for the death of her daughter Myrcella. Cersei is pleased and, in turn, promises to grant his request of marriage after the war is won. Euron then steps away from the Iron Throne towards Jaime, deliberately provoking him about the fact that Cersei is going to marry him. Euron is eventually ordered to set sail again and leads the Iron Fleet west to Casterly Rock where he attacks and destroys the remainders of Daenerys' fleet who are besieging the Rock.
While Euron and Cersei take part in the Dragonpit Summit, the entire Iron Fleet is docked in Blackwater Bay. After Euron witnesses a wight firsthand, he claims to be leaving in fear and taking the Iron Fleet back to the Iron Islands. However, Euron secretly takes the Iron Fleet to Essos under Cersei's orders with the intent of transporting the Golden Company to Westeros to fight for Cersei.
The Iron Fleet successfully ferries the Golden Company to Westeros and anchors in Blackwater Bay while Euron courts Cersei. That night, Theon Greyjoy leads an incursion onto the Silence to free his sister Yara. After successfully doing so, the siblings sail their three ships towards the Iron Islands, intending to recapture them.
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