Battle at Dragonstone

The Battle at Dragonstone is an engagement during Daenerys Targaryen's invasion of Westeros when Euron Greyjoy and a portion of the Iron Fleet ambush Daenerys Targaryen's fleet while they are sailing back to Dragonstone from the North.

Prelude
"We have won the Great War. Now we will win the last war."

- Daenerys Targaryen

Daenerys Targaryen officially suspended her campaign to take the Iron Throne from Cersei Lannister after the Dragonpit Summit, where House Targaryen and House Stark agreed to an armistice with House Lannister. After meeting with her brother Tyrion, Daenerys's Hand, Cersei further agreed to send the Lannister armies north to fight in the Great War against the Night King and his White Walkers and their army of the dead, which Daenerys had previously agreed to help Jon Snow with. After Daenerys and Jon set sail for the North, however, Cersei revealed to her brother Ser Jaime that she did not truly intend to honor the truce, and instead hired the Golden Company to restrengthen her position and take back the southern kingdoms. Intending to honor the promise he made to fight for the living, Ser Jaime abandoned his sister and rode north alone.

The Golden Company, led by Captain Harry Strickland, was ferried across the Narrow Sea from Essos to Westeros on the Iron Fleet by Euron Greyjoy, Cersei's new ally, the self-proclaimed King of the Iron Islands. The living ultimately prevailed, albeit narrowly, over the dead at the Battle of Ice and Fire with the destruction of the Night King at the hands of Arya Stark, shattering the White Walkers and destroying the wights. With the Great War having been declared won for the living, the survivors refocused their efforts towards the last war: taking the Iron Throne from Cersei and House Lannister.

After holding a massive funeral for the fallen and celebrating their victory at Winterfell, Daenerys, Tyrion, Varys, Grey Worm, Missandei, and the remaining Unsullied marched to White Harbor and set sail to return to Dragonstone while Jon Snow, the armies of the North and the Vale, and the remaining Dothraki marched south on the Kingsroad towards King's Landing.

The ambush
Tyrion Lannister and Varys discuss the implications of the parentage of Jon Snow, having learned from Sansa Stark, who, alongside Arya Stark, learned straight from Bran Stark with Jon's permission, that he is Aegon Targaryen, the son of Daenerys's brother Rhaegar Targaryen and Lyanna Stark. Daenerys, meanwhile, flies overheard on Drogon with an injured Rhaegal next to them when suddenly Rhaegal is struck with three bolts from an anti-dragon scorpion, causing him to plummet and sink into Blackwater Bay. A portion of the Iron Fleet is revealed to have been sitting at Dragonstone with Euron Greyjoy himself at its command. Each of the ships are equipped with an anti-dragon scorpion. Daenerys directs Drogon to attack the ships, but pulls back when Euron and the ironborn fire again, not taking the bait. However, after they fly away to safety, Euron and his men target the Targaryen fleet and fire on the ships. Tyrion jumps into the water to escape.

Aftermath
The survivors of Euron Greyjoy's surprise attack are able to swim ashore to Dragonstone, among them Tyrion Lannister, Varys, and Grey Worm, but Missandei is taken captive by Euron, who returns to King's Landing and delivers her as a hostage to Queen Cersei Lannister. Daenerys Targaryen and Drogon also return to Dragonstone. Daenerys wants to march on King's Landing and destroy the city to avenge Rhaegal and save Missandei, but Varys reveals that Cersei has brought the smallfolk into the Red Keep to hold as hostages, knowing that Daenerys and Tyrion do not want to kill innocent civilians.

Word of the ambush reaches Winterfell. Ser Jaime Lannister learns of the ambush and Daenerys's plan to march on the capital from Sansa Stark and Brienne of Tarth. Later at night, Ser Jaime decides to ride south to try and rescue Cersei, believing he has no other choice, leaving Brienne behind at Winterfell.

Daenerys parleys with Cersei outside the gates of King's Landing. Hand meets Hand as Tyrion and Qyburn, who designed the anti-dragon scorpions, discuss their opposing queens' surrenders; Tyrion tries but fails to appeal to Qyburn's humanity to save thousands of innocent people, and pushes forward to talk with his sister. Tyrion tries to convince Cersei to surrender in order to save her unborn child, appealing to his sister's love for her children, but Cersei does not give in. Cersei then has Ser Gregor Clegane behead Missandei before Daenerys, Tyrion, and Grey Worm. Daenerys angrily walks away from the parley.