- Tyrion: "I remember reading an old sailor's proverb: Piss on wildfire and your cock burns off."
- Hallyne: "Oh...No, I've not conducted this experiment. It could well be true; the substance burns so hot it melts wood, stone, even steel! And of course: flesh. The substance burns so hot it melts flesh like tallow."
- — Tyrion Lannister and Wisdom Hallyne[src]
Wildfire is identifiable by the distinctive green hue of its flames and a bright green color in its liquid state. Pyromancers refer to it as "the Substance", while in the lowest circles it is derisively referred to as "pyromancer's piss".
Thanks to his reluctant agent, Lancel Lannister, Tyrion is alerted to Cersei's plan to use wildfire in the defense of King's Landing against the impending attack by Stannis Baratheon by catapulting it against Stannis's fleet. To confirm if this plan is actually being prepared for, Tyrion and Bronn, Commander of the City Watch, visit Wisdom Hallyne of the Alchemists' Guild. Bronn derisively says he doesn't believe the pyromancers' claims about wildfire, as there are always charlatans on the side of battlefields selling "pig shit" to soldiers and claiming it has magical properties. Hallyne insists that the abilities of wildfire are indeed very potent. Bronn then points out that even if this is true, wildfire is too unstable to be used safely in catapults by inexperienced troops: the moment one of the catapult teams drops a single jar, it could burn the whole city to the ground by accident. Hallyne then opens the guild's vault to reveal to an awed Tyrion that they have amassed over 7,800 jars of wildfire, enough "to lay King's Landing low". Tyrion agrees and commands Hallyne to begin producing wildfire for his purposes instead of Cersei's.
While discussing the defense of the city with Varys and Bronn, Tyrion identifies the Mud Gate as the city's most vulnerable spot and the most likely location for Stannis to attempt a landing. Tyrion resolves to make a stand there. When Varys asks him what can they use to defend the city, Tyrion replies "pig shit".
When Stannis Baratheon's fleet arrives at Blackwater Bay, Ser Davos Seaworth (commanding the vanguard of the assault) is perplexed to see only one ship from the royal fleet emerge to challenge them. He realizes the ship is unmanned so he halts his archers, but then sees the ship is emptying wildfire into the bay from pipes at its rear. Tyrion had all eight thousand jars of wildfire loaded into the ship. At Tyrion's command, Bronn fires a burning arrow into the wildfire, which detonates the ship in a massive explosion that pulverizes Stannis's ships closest to the blast. The spreading fire engulfs most of the remaining fleet. Hundreds, if not thousands, of sailors and soldiers under Stannis's command are burned alive. Stannis continues his attack on King's Landing but with the losses from the explosion, he loses the battle and is forced to retreat to Dragonstone on one of his few remaining ships.
While touring the Great Sept of Baelor with Margaery Tyrell, King Joffrey Baratheon points out an urn containing the ashes of Prince Aerion Targaryen who died drinking wildfire, believing that the substance would turn him into a dragon (Aerion was wrong).
While convalescing at Harrenhal, Jaime Lannister reveals to Brienne of Tarth that the real reason he killed Mad King Aerys II Targaryen is because he ordered the entire capital city to be burnt to ashes by wildfire, rather than let it fall to the rebels. When it began to appear that the rebels would win the war, the Mad King had his pyromancers hide caches of wildfire all over King's Landing - under the Great Sept of Baelor, under the slums of Flea Bottom, under houses, stables, taverns, and even under the Red Keep itself. After the Battle of the Trident, the rebels started to march on King's Landing. Before the rebels arrived, Tywin Lannister arrived at the capital city at the head of a Lannister army, ostensibly as reinforcements to defend King's Landing but as soon as the Lannister army was inside the gates they betrayed the Targaryens and proceeded to sack the city. The Mad King, seeing his defeat was imminent, ordered Wisdom Rossart to light the wildfire and burn the entire city and all of its half a million inhabitants to ash, convinced (somewhat like Aerion Brightflame) that he would not burn but that the flames would transmute him into a dragon to destroy his enemies. After the Mad King gave this suicidal order, Jaime realized he could not allow it to happen. First, he killed Rossart before he could transmit the Mad King's order to the rest of the Alchemists' Guild. Then he killed the Mad King in front of the Iron Throne. Eddard Stark entered the throne room to witness Jaime kill the king he vowed to protect as a member of the Kingsguard. Jaime did not tell Eddard or anyone else why he killed the Mad King, thinking that no one would believe him. Subsequently, Jaime was branded a "Kingslayer" instead of the person that saved the entire city.
The exploding wildfire in Bran's vision is not from the past during the the Mad King's reign but instead is from the future. Cersei Lannister and Qyburn use wildfire, presumably the wildfire the Mad King had ordered to be placed under the Great Sept of Baelor as part of his long ago wildfire plot, to destroy the Great Sept on the day of Cersei's trial for her role in the death of her husband, King Robert Baratheon. The explosion kills all of those inside and surrounding the sept, including the High Sparrow, the Most Devout, the Faith Militant, many nobles, and most of House Tyrell including Queen Margaery Tyrell as well as a massive amount of civilians in the area around the sept. Cersei's son, King Tommen I witnesses the explosion in his room high in the Red Keep and quickly commits suicide by jumping from his window. Soon after, with no one left to challenge her, Cersei is crowned Queen of the Andals, the Rhoynar, and the First Men by Qyburn in the Red Keep.
Behind the scenes
- In the German dub, "Wildfire" was renamed to "Seefeuer" which means "sea fire", one of the Byzantine names for Greek Fire. Wildfire (and for that matter, Greek Fire) aren't exclusively used in naval combat, though they are very effective against wooden ships.
- In the Spanish dub it is called "Fuego Valyrio", i.e. Valyrian Fire, despite not being actually related to the Valyrian Civilization.
In the books
In the A Song of Ice and Fire novels, wildfire is a very unstable material: It is highly combustible and can be set alight even by bright sunlight. It is described as having an emerald green coloring once ablaze, which is so strong that it can turn the air around it green.
Wildfire is similar to real-life napalm or Greek fire, both highly combustible liquids used in combat. Greek fire was famously believed to be used by the Byzantine Empire throughout its history (roughly the 4th to the 15th Centuries CE), and so may have been a technology known to medieval peoples.
Wildfire's use under controlled conditions was popular with some members of House Targaryen and some worshipers of the Lord of Light. For example, Thoros of Myr coated his sword with a thin layer of wildfire and then set it ablaze to scare his enemies in combat. This earned him the enmity of Tobho Mott, since this practice completely ruined even the best-made swords.
The alchemists refuse to divulge how wildfire is created, claiming that it is done with magical spells (a claim dismissed by others, particularly the maesters). Wildfire is stored in clay pots in bare stone cells under the Alchemists' Guildhall in King's Landing. Each cell is built under a chamber full of sand, which can be emptied into the cell below to extinguish the fire in case of accidents. Wildfire grows more volatile with age and can only be disposed of through hazardous means.
- Wildfire on A Wiki of Ice and Fire (spoilers from the books)
- Greek Fire on Wikipedia
- Hellburners on Wikipedia