"Burn them all!" So screamed King Aerys II Targaryen, over and over, in his final hours. At the time, Robert Baratheon was coming closer to sacking the Iron Throne. Aerys intended to preemptively retaliate by burning the entirety of King's Landing with a volatile green substance called "wildfire." Thousands of barrels of wildfire were placed underneath King's Landing.
Aerys never got a chance to follow through with his dastardly plan. Jaime Lannister (Nicolaj Coster-Waldau) killed him. But years later, Aerys' daughter, Daenerys (Emilia Clarke), fulfilled his final mission. As Daenerys sacked King's Landing in season 8, episode 5 of Game of Thrones, officially called "The Bells," poufs of green fire intermingled with Drogon's flames — that green substance is wildfire, and it's far more dangerous than any other weapon seen in Game of Thrones. With that, Daenerys is officially one step closer to becoming her father.
Wildfire is even more flammable than a Drogon's flames — or any dragon's. As Hallyne, a character in George R. R. Martin's novels, explains to Tyrion, "Once it takes fire, the substance will burn fiercely until it is no more. More, it will seep into cloth, wood, leather, even steel, so they take fire as well." Also, wildfire is virtually impossible to quell: The green fire burns so hot not even water can extinguish it.
It's only fitting that wildfire be part of Daenerys' most violent attack, which she spearheaded singlehandedly. Simply put, wildfire is the Targaryen way. After their dragons died, Targaryens used wildfire (and the threat of it) to hold onto power. As we've seen firsthand in Game of Thrones, wildfire is a more consistent and controlled than dragon fire — therefore more useful for wars and minor rebellions. The Targaryens became patrons of the Alchemists' Guild, the order of magicians who created wildfire.
However, wildfire is not exclusively a Targaryen weapon. Wildfire has been deployed in certain key battles of Game of Thrones. In a moment of incisive strategic thinking, Tyrion used wildfire during the Battle of Blackwater. Then, Cersei used King Aerys' leftover barrels of wildfire to blow up the Great Sept of Baelor and kill her enemies in one fell swoop (we remember you, Margaery).
As this episode of Game of Thrones demonstrated so brutally, Cersei didn't use all the wildfire up during her attack on the Sept. There were still barrels of wildfire scattered in underground corridors throughout King's Landing leftover from Aerys' plot. Drogon's flames ignited the barrels, causing wildfire explosions — all of that green fire.
There is nowhere safe in King's Landing during Daenerys' siege. She is as merciless as her father. She begins the raid after the bell of surrender had already rung, killing innocents with dragon fire and eventually wildfire.
The brutal attack echoes her father's words, pulled from A Storm of Swords: "The traitors want my city, but I'll give them naught but ashes. Let Robert be king over charred bones and cooked meat."
But Daenerys' attack is even more severe than her fathers'. Unlike her father, she has both the Targaryen staples of dragons and wildfire; also unlike her father, she actually gets around to using those weapons. By the time Daenerys is done with King's Landing, there isn't much left other than "charred bones," "cooked meat," and a very determined Arya Stark. Is the Iron Throne even intact after the onslaught?
Daenerys has never been as much as a Targaryen as she was in this episode: Dragon beneath her, wildfire below her, and mercy not in her vocabulary. Sure, Daenerys may not be the rightful inheritor to the throne now that we know Jon's true parentage. But as she burns down King's Landing, she might also burn down concepts like "rightful inheritor" and "succession," until there's nothing but her, her dragon, and fear. Wild, indeed.