WARNING: Spoilers for Game of Thrones season 8, episode 5.
As Daenerys razed King's Landing with Drogon and his orange fire breath in Game of Thrones season 8, episode 5, there were also explosions of green wildfire. This is a reference back to an old plan of Cersei's and the show acknowledging a long-held fan theory even as it disproved it.
Wildfire is the thick, green liquid with highly explosive properties. It was first introduced in Game of Thrones season 2 and used by Tyrion Lannister to hold off Stannis Baratheon's invading fleet at the Battle of Blackwater Bay. It made a return in season 6 when Cersei used it to blow up the Sept of Baelor and the High Sparrow (along with most of House Tyrell) with it. And, evidently, it still had a small part to play in season 8 as well.
There's a very simple reason why there was wildfire during the Battle of King's Landing in Game of Thrones season 8, episode 5. When plotting against the faith militant, Cersei had pockets of wildfire dispersed throughout the Westeros capital. These were finally activated by Drogon's dragon fire.
With so much going on in Game of Thrones season 8 - especially this post-Night King era - and criticisms of overly broad storytelling, it's nice to see the show remember one core aspect of the world and bring it back, even in the background.
Of course, to many Game of Thrones fans, it will be surprising to see wildfire used in such a passing way. One of the most popular theories about the story's endgame was that Queen Cersei, mad with power, would attempt to blow up King's Landing, only for her brother, Jaime, to stop her; this would have mirrored Jaime's murder of King Aerys decades earlier, bringing his arc full circle. In the end, though, Jaime and Cersei died in each others' arms as the Red Keep collapsed on them from above.
There's two very good reasons why that didn't come to pass, in the Game of Thrones show at least. The first is that Cersei having already pulled that trick in season 6 would reduce the shock value (similar to Lady Stoneheart being cut making Jon's resurrection more surprising). The second is that it had to be Daenerys who destroyed King's Landing - she is now the Mad Queen and the ultimate show of that is her burning the city with her one remaining dragon, honoring Missandei's final words.
Game of Thrones concludes next Sunday on HBO at 9pm.