History is everything in “House of the Dragon” and those who don’t learn from it … well, you know how the saying goes. No location in all of Westeros provides a starker example of this than Harrenhal, which has stood as a lasting reminder to never mess with the Targaryens and their dragons. Built as the largest and mightiest fortress in all the land, King Harren “the Black” named it after himself and made this his home 300 years prior to the events of “Game of Thrones,” back when the Seven Kingdoms truly had that many rulers and kings (and more!) all vying for power … until they were invaded by Aegon Targaryen and his sisters during the era that would become known as the Conquest.
While other lords either died fighting or bent the knee to the unstoppable might of three full-grown dragons, Harren decided to put his trust in the strength of Harrenhal to outlast any attack that Aegon could throw his way. As you can probably imagine, that didn’t go so well when Aegon merely mounted Balerion the Black Dread (whose massive skull we’ve seen in both “House of the Dragon” and “Game of Thrones” before) and literally roasted the defenders within, melting the very castle itself and forever casting a pall over the surrounding area.
Even if that were the last notable instance of Harrenhal popping up in Westorosi history, it would’ve remained an example for everyone to learn from … but that was only the beginning of the bad luck attributed to the castle and those unfortunate souls who would dare to take up residence as castellan of Harrenhal.