Euron is the younger brother of King Balon Greyjoy, older brother of Aeron Greyjoy, and the eldest uncle of Theon and Yara Greyjoy.
Euron Greyjoy is the younger brother of Balon Greyjoy, head of House Greyjoy, Lord Reaper of Pyke and self-fashioned King of the Iron Islands.
Euron has spent the last few years as a pirate, reaving from Oldtown to Qarth and beyond. He once lost his senses during a storm whilst sailing on the Jade Sea, and his crew was forced to tie him to the mast to prevent him from jumping overboard. When he was let down after the storm, he had all their tongues ripped out.
Tyrion Lannister tells Theon about his memories of witnessing the Raid on Lannisport which Tyrion says was caused by Theon's uncles
Euron returns to the Iron Islands following the War of the Five Kings, arriving during a violent storm. He confronts Balon, who believed Euron to be dead, on one of the rope bridges of Pyke, saying the ironborn words of “what is dead may never die”. When Balon accuses him of mocking the Drowned God, Euron retorts, boasting that he is the Drowned God, for whenever men see his sails they pray. Balon notes that Euron lost his mind during a storm, and Euron tells him that he is “the storm”, prompting Balon to attack him with a knife. Though Balon wounds his face, Euron easily overpowers his elder brother, and throws him off the bridge to his death.
Euron sails the Iron Fleet to King's Landing, answering the invitation of Cersei Lannister, the new Queen of the Seven Kingdoms. Cersei proposes an allegiance between the crown and the Ironborn, which Euron counters with an offer of marriage. Cersei declines Euron's attempt at courtship, and he departs, promising to return with a gift that will win her heart.
Seeking out his promised gift for Cersei, Euron intercepts and attacks Yara's fleet, which had departed from Dragonstone and was sailing to Dorne to consolidate the Dornish armies and fleet. The Silence locks onto Black Wind with a corvus, and Euron's men board and attack Yara's and Theon's. During the ensuing battle, despite taking several wounds Euron kills Obara Sand by impaling her with two swords and her sister Nymeria Sand by strangling her with her own whip. Soon afterwards, he engages in a melee with his niece and beats her, holding her at her throat with his axe. He calls for his nephew, mocking him as "little Theon" and as a "cockless coward," and implores that he come rescue her. However, Theon instead jumps overboard, leaping into the sea, which Euron sadistically laughs at. Theon holds onto a plank in Blackwater Bay, watching on as the Silence and the rest of Euron's fleet sail away while his sister's fleet burns and sinks to the bottom of the Blackwater.
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. Cerse 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.
Euron is present in the Dragonpit at the Parley in King's Landing sitting by Cersei. When Tyrion begins the discussion, Euron interrupts him and taunts him and his nephew Theon. He warns that if Theon doesn't submit to him, he will kill Yara, who remains his hostage. A silence falls between the rest of the attendants due to Euron's outburst, and Jaime and Cersei tell Euron to sit down or leave. After Sandor Clegane releases the wight, Euron watches Jon Snow's demonstration on how to destroy it. He walks up to the wight and says how this is the only thing that truly terrifies him, and that he plans to sail home to the Iron Islands with the Iron Fleet. He advises Daenerys Targaryen to do the same on Dragonstone so that they are the only ones left after winter ends. Cersei later privately reveals to Jaime that Euron is in fact on his way to Essos to harbor the Golden Company back to fight for her.
Balon Greyjoy’s younger brother Euron returned from years at sea to claim the Iron Islands as his own – by killing his brother. He unapologetically confessed to the murder at the kingsmoot, and was still elected King of the Iron Islands. His plan to seduce Daenerys Targaryen with the Iron Fleet was stymied when his niece Yara and nephew Theon allied with her instead. To prove his worth to Cersei, Euron ambushed Dany’s fleet and presented Ellaria and Tyene to Cersei for execution. Upon seeing the wight Jon Snow brought to the capital, Euron seemingly retreated to the Iron Islands.
Euron is a wildly unpredictable and cruel man, the most feared pirate alive, who has become the terror of the world's oceans from Oldtown to the Jade Sea. Even many of the other ironborn greatly fear Euron, and consider him to be half-insane - not in the sense of being impulsive, but in that he seems almost delusional, with an utterly fearless, warped personality. Euron is not prone to outbursts of anger or impulsive violence: everything he does seems to be for some sort of calculated purpose, though others might not be able to perceive it - such as calmly ripping out the tongues of his entire crew for no other reason than "I needed silence". Euron possesses an unnerving coyness to him, tranquil and detached in the face of danger and mildly playful (but never indulgent in idle whims). When walking along the rope-bridges of Pyke during a massive storm, while Balon struggled not to fall over, Euron calmly stood his ground without bothering to hold on to anything. Euron also isn't particularly arrogant, in the sense that he doesn't have a sense of entitlement - he just does what he feels like, and is self-assured in his own power and abilities.
In contrast, Joffrey Baratheon was an arrogant, petty fool prone to random outbursts of anger, obsessed with the title of king he believed he inherited, even though he was little more than a puppet backed up by his grandfather Tywin. Joffrey never actually wielded a weapon, however, usually making a cowardly retreat when confronted with real danger. Ramsay Bolton was sadistic and personally dangerous, capable of great violence and torment against people he had already captured, but he didn't have any true authority to back it up, and an impulsive, childish need to brutalize people for transient amusement (i.e. hunting women for sport and flaying men alive who disobeyed him, then leaving them on public display) with no thought to the long-term repercussions. Ramsay only knew random force and was in no way skilled at diplomacy, alienating potential allies. Euron Greyjoy, meanwhile, isn't impulsive but capable of cunning long-term strategies, and unlike both of them, is actually capable of being extremely charming when the situation arises. Euron needed to win over the ironborn to elect him king willingly, playing to their admiration for strength and audacity, while making grandiose promises. In many ways, Euron is the feared ruler that Joffrey and Ramsay wished they could be: genuinely dangerous and cunning, with a well-earned reputation, the authority to back it up, and a gift for long-term manipulation.
Euron's true personality, however, is in some ways difficult to pin down - he is such a master manipulator that he tailors each performance, as it were, to fit his current audience. When he wins over the ironborn at the Kingsmoot, he shifts to a more low-brow register, playing to their love of battle and crass sex jokes. When he appears before Queen Cersei, however, he shifts to a different act of a swaggering and dangerous but very witty and charming persona. His private confrontation with his brother Balon may have been one of the few times he dropped the mask and the man underneath appeared: dark and threatening, making a few bitter quips, but with an unnerving sense of tranquility while making blasphemous claims about his own power, likening himself to a god, and to the storm itself.
Euron is a terrifying and relentless warrior in personal combat if the need arises, laughing while shrugging off minor stab wounds. He is a master combatant, individually killing two of the sand snakes and capturing his niece; all of whom were deadly warriors in their own right.
Euron also has no qualms with other social taboos such as kinslaying, openly killing his own brother to seize the throne and bragging about that in public, and flippantly announcing he will murder his niece and nephew. In that aspect, Euron proves to be worse than Ramsay: Ramsay has also killed his kin, but even he wouldn't admit that in public.