The world of Yu Yu Hakusho is full of strange and dangerous things. Throughout the series, viewers are introduced to many magical attacks, from small aura blasts to powerful techniques that decimate whole areas. However, one move stands out among the rest, and this attack is Hiei's Dragon of the Darkness Flame technique.
This technique is infamous in-universe as several different masters are said to have tried and failed to summon and wield it properly. Like a piece of folklore, those using the Dragon of the Darkness Flame harness the power of the Darkness Flame that dwells deep in the Demon World. However, while it is unknown how Hiei learned of the technique or how to attempt it, the powerful attack became an unforgettable one.
As the name suggests, this attack involves a giant dragon. Hiei exposes his arm by removing the magical cloth he keeps his arm wrapped in to perform this powerful maneuver. He then focuses his demonic energy and opens his Jagan Eye as he siphons energy up from the Demon World and forms it into a dark, fiery dragon. As this happens, strange weather effects may occur around Hiei as the sky turns blood red, with black lightning and flickering pillars of light erupting from the ground. Once this attack is fully charged, a long black dragon made out of black flames forms around Hiei's arm.
Once this stage is reached, the attack is ready to launch. Hiei extends his arm out, and the dragon shoots forward, charging in the direction Hiei points. As the dragon moves forwards, it utterly destroys anything it comes into contact with since it is made out of demonic flames -- meaning that it consumes anything it touches, sending them straight to oblivion. However, the dragon does have a mind of its own, and once it is released, it can not be easily controlled. If the dragon does turn around and hit Hiei, he can absorb the energy from the dragon and use it to boost his other powers for a short time. Thus, giving this powerful attack a secondary utility function. However, after absorbing the dragon, Hiei does need to hibernate for a while, forcing him to use it strategically.
However, this attack does have some drawbacks. The sheer amount of power involved can cause the attack to backfire, hurting or even killing the user during the summoning process. For example, Hiei's first attempt to use the Dragon of the Darkness Flame backfired terribly. The intense heat of the flames seriously burnt Hiei's forearm. If it wasn't for Ruka's forcefield partially healing him, Hiei's arm might have been left permanently unusable, if not totally destroyed. Thankfully for the heroes, Hiei was able to use his Jagan to heal his arm. Still, Hiei decided that he would go and learn how to control this power to use it without harming himself.
Once this training was complete, Hiei was able to control the dragon much easier. Hiei did this by compressing and sealing the dragon in a dragon-shaped tattoo on his arm, making the energy easier to handle. In fact, when Hiei uses the technique after getting the tattoo, the weather seems to be unaffected by it, suggesting that it is a side effect of Hiei's lax control of the dragon. However, training does not reduce the dragon's power, and this technique still utterly destroys anything that dares get close to it without knowing a counterattack.
One of the most impressive uses of the Dragon of the Darkness Flame came during Hiei's fight with Team Rokuyukai member Zeru. As this is the first time Hiei summons the dragon, its destructive power is clear to see. When Zeru gets hit by the attack, he is instantly destroyed, leaving only a black silhouette where he once stood. Another fascinating fight is Hiei's battle against Mukuro. Mukuro is one of only a few people who could stop the dragon -- destroying it without getting hurt -- making it clear that those who are mightier than Hiei could counter the rampaging beast.
The Dragon of the Darkness Flame is one of the most fascinating techniques in Yu Yu Hakusho, and it makes Hiei -- already a fan-favorite character -- an even more memorable combatant. And the first use of the move gave us a legendary moment that has transcended time and cemented itself as one of the most epic moments in anime history.