The blue flames of Fire Nation princess Azula bear special significance in the world of Avatar: The Last Airbender because they’re one of the few types of bending which Aang and his various reincarnations cannot imitate. Like the telepathic fire bending of Sparky Sparky Sparky Boom Man, floating ability of Zaheer and (The Legend of Korra notwithstanding) metal-bending power of Toph, Azula’s embers are not only a trademark of her explosive personality, but a testament to her truly intimidating talent as a fire bender.
But why, exactly, is she alone capable of producing this unique color of flame? Well, in order to answer that question, we better take a step back and ask what kind of person Azula is in general. First introduced toward the end of the first season as the younger sister of Zuko, she quickly established herself as one of the deadliest and most terrifyingly persistent enemies that Team Avatar ever faced.
Azula got that reputation through a potent mix of her cold character and relentless combat skills, two qualities which turn out to be closely related. Born with an obscene amount of natural talent, Azula grew up being able to achieve whatever goal she set for herself by sheer threat of force. This inborn strength, combined with the arbitrary one that she received by virtue of being the child of a dictator, led her to believe she was the center of the universe.
And that really is all there’s to it when it comes to understanding Azula. Although fans have considered several theories as to why the feared Fire Nation princess is the only one who can conjure up blue fire, they’re dodgy and unsubstantiated at best. In truth, the creators never offer an explanation for Azula’s ability, and did so in order to stay true to her character.
While Azula’s interior life was explored at the very end of the series, the initial seasons of Avatar: The Last Airbender treated her, first and foremost, as a foil to Zuko, whose confidence suffered at the hands of his younger sister’s insurmountable, seemingly God-given strength.