In House of the Dragon season 1, episode 7 "Driftmark," Prince Aemond Targaryen claims the largest dragon in the Seven Kingdoms but loses an eye in a fight that breakouts between him on one side and Daemon's girls and Rhaenyra's sons on the other. His grandfather and Hand, Otto Hightower knows Vhagar is an asset to the Greens, remarking, "What that rogue Aemond has done in winning Vhagar to our side... the boy was right. It's worth a thousand times the price he paid."
Upon hearing these words, Aemond's mother, Alicent Hightower, who's otherwise mourning the loss of her child's eye, feels somewhat assured. By claiming the largest dragon in the world, young Aemond makes a great stride towards the Greens' victory in the inevitable war of succession that is to break out between King Viserys' scions from two wives.
The serpentine House of the Dragon beast, Vhagar is a she-dragon and has been gracing the skies of Westeros since the time of Aegon the Conqueror. Vhagar, as a matter of fact, was Aegon's older sister-wife, Visenya Targaryen's mount during and after the Conquest. She was among the three dragons that the Targaryen siblings brought to Westeros during their invasion. Aegon's Balerion the Black Dread died of old age during King Jaehaerys I Targaryen's reign, Rhaenys' Meraxes was downed by an arrow in the First Dornish War but Vhagar lived. Aegon's victories rested on the might of the three dragons, and while he and his sister-wives used the beasts to pour fire on enemies in pivotal battles such as Field of Fire, the dragons also served as deterrents in regions such as the Vale. Given that Vhagar is a battle-hardened dragon, its rider Aemond has every right to boast, "'Tis I... who rides the largest dragon in the world..."
Vhagar's Birth And Riders
Vhagar was hatched on Dragonstone during the chaotic period that followed the Doom of Valyria, i.e., the Century of Blood. Named after a god of the Valyrian Freehold, Vhagar's known riders after Visenya include Prince Baelon Targaryen. The she-dragon also bonded with Lady Laena Velaryon who commanded the beast to burn her alive once she realized she was sure to die in childbirth. Besides Aegon's Conquest, Queen Visenya used Vhagar in the two-year-long punitive campaign against the Dornish known as Dragon's Wroth. Those two years saw Aegon and Visenya burn every Dornish stronghold except Sunspear and its shadow city in retaliation for Queen Rhaenys' assassination in the First Dornish War. Vhagar would also go on to light the funeral pyre of Aegon the Conqueror in 37 AC.
The she-dragon also played a part in the Faith of the Seven's insurgency known as the Faith Militant uprising in Game of Thrones lore. The insurgency arose because the Faith viewed Targaryen marriage practices as unacceptable and an abomination. Members of the Faith waged an armed rebellion when Aenys II wed his daughter, Rhaena to his son, Aegon. The uprising continued through Maegor's reign who knew no response except going on the offensive. During the Faith Militant uprising, Queen Visenya's Vhagar set fire to the seats of minor houses namely Blanetree, Deddings, Lychester, Terrick, and Wayn in the Riverlands in a single night. Thereafter, Vhagar became riderless and remained so for twenty-nine years when Visenya died of a sudden illness in 44 AC. The she-dragon remained on Dragonstone and later in the Dragonpit in King's Landing until Baelon the Brave claimed her.
Vhagar, Caraxes, and Vermithor were used by the Targaryens in the Fourth Dornish War and when Balerion died in 94 AC, Vhagar was the only-remaining dragon of Aegon's Conquest (likely to be an upcoming Game of Thrones prequel). As seen in House of the Dragon, Vhagar was still in mourning at Driftmark when young Aemond Targaryen claimed her. She's almost as big as Balerion was during the Conquest, and currently, the oldest dragon to fly Westeros' skies. While Vermithor and Daemon Targaryen's Caraxes are gigantic beasts, Vhagar remains unmatched.
Vhagar In The Dance
Vhagar was seen in House of the Dragon season 1, episode 10 "The Black Queen," outside Lord Borros Baratheon's fortress of Storm's End. Vhagar's rider, Aemond was inside and had beaten the Black faction in securing Lord Borros' support. Lucerys Velaryon, who flew to Storm's End on dragonback as his mother, Queen Rhaenyra's messenger was shown the door. While riding away, Lucerys' uncle, Aemond chased him on dragonback in the skies above Shipbreaker Bay. Because Arrax breathed fire at Vhagar, the latter got out of control and defied her rider by the end of the chase. Just when it looked like Lucerys and Arrax were out of danger, Vhagar caught them and killed Lucerys in midair.
Vhagar's rage and aggression bring into focus what the late King, Viserys I Targaryen said to his daughter, Rhaenyra early on in House of the Dragon: "The idea that we control the dragons is an illusion. They're a power man should never have trifled with. One that brought Valyria its doom. If we don't mind our own histories, it will do the same to us." Viserys' words are an excellent example of foreshadowing because, in the Dance of the Dragons that's officially kicked off, the power tussle will crumble the mighty Targaryens into pieces and nearly decimate the illustrious house.