Appearance
Hiei is a midget with huge hair. He stands at 4'10, and his hair is at least half a foot tall, and always sticks up. The shape of it is a bit like a feather, with rounded sides coming to a point. His hair is black, with several shorter spikes in the front that are set off with a white border.

Despite his height, however, Hiei is muscular, with a lean athletic build typical of an anime character. His eyes are a deep red, and have more of a catlike shape to them, with small irises. His body has two very distinguishing marks: the most notable is a black dragon "tattoo" that starts on the back of his right hand, and winds up his arm to about his elbow. This, however, is almost always kept underneath a bandage. The second mark is a slit in the middle of his forehead, which is actually the lid to his third eye, called a Jagan, which has a large purple iris. Again, however, the slit is kept hidden, in this case under a white headband.

Hiei typically wears a pair of black pants that are a bit baggy, and that cuff at the bottom. He also wears a pair of black boots. Occasionally, Hiei will also wear a no-sleeve blue shirt. Over this, he will wear a long wrap around cloak that is black on the outside and red underneath. This cloak is form-fitting at the waist, comes down about to his shins, and has long sleeves, so serves as more than adequate outerwear. He can also keep his katana and sheath completely hidden beneath the cloak.

Physical Powers
Speed: Hiei is easily the fastest main character in the series, able to move faster than the human eye can detect even at his first appearance in the series. By the I've picked to take him from, he's become even quicker, so much that it takes an extremely high level demon or human to be able to see his movements. He can trick people by moving so fast that he leaves an afterimage of himself.

Jumping: While he can't fly, you wouldn't be able to know it. Related to his speed, Hiei has the ability to take multiple quick leaps, covering vertical distances no ordinary human could.

Strength: Nothing too special; he's just significantly more powerful than a normal human.

Sensing: Like all supernaturally powered creatures in his series, Hiei can detect whether a creature is human or not, and can tell the strength of their Reiki, or spiritual energy. Notably, however, reiki can be disguised or hidden, and talented demons such as Hiei can even manipulate reiki so it can be followed like a trail. Hiei's sight is particularly good as well, as he can see movements that are often indiscernible to everyone else without the use of slow-motion replay.

Jagan Powers
Telepathy/Mind Control: While it's never shown that he can read thoughts, Hiei can project his thoughts into the minds of others. The Jagan also has the power to control the minds of others, especially weaker demons and humans.

Sensing: In addition to the basic sensing every creature with an ounce of spiritual awareness in the series can do, Hiei's Jagan allows him to pinpoint certain creatures over great distance, enabling him to find them. This can, however, be prevented if the creature is kept behind enchanted talismans.

Multiple Eyes: In his "true form" (which we only see during his first fight and in the movie), multiple eyes open all over Hiei's body, acting as amplifiers for his strength and speed.

Fists of the Mortal Flame: Hiei can summon the spectral flames of the human world, surrounding his fists with their energy to make his punches more devastating.

Sword of the Darkness Flame: Hiei can also summon spectral flames of the demon world, blending them and his own yoki (demon energy) to create a sword made of fire that not only burns, but is sharp. For this, he has to channel his yoki into an object, such as a sword handle. Notably, Hiei does not like using this attack at all, stating that it's devoid of any sense of artistry or creativity…basically, that it's beneath him.

Dragon of the Darkness Flame: By far, this is Hiei's most powerful and devastating attack. By channeling enough yoki into his arm, Hiei can summon a dragon of flame from the demon realm, which he can then propel at a victim. The dragon is massive, easily able to cause huge amounts of death and destruction. However, an opponent with enough strength can turn back the dragon, at which point it goes after Hiei. This isn't in their best interest, however, as the true strength of this attack is when Hiei absorbs the power into his own body, giving himself an unbelievable power boost. Hiei himself describes it as a nutrient for the user. The downfall of this attack is that after it is used, Hiei must immediately "hibernate" for several hours to restore the lost energy…with stress on immediate, as he can't keep from passing out. The power of this attack is kept in Hiei's right arm, which is marked with a dragon. To keep this power contained, Hiei wraps his arm in enchanted bandages.

Notably, everything listed under "Jagan Powers" can only be used when Hiei's Jagan is open and not blinded by some foreign substance. To contain the power of the Jagan when not in use, Hiei wears an enchanted headband.

Hiei also has very honed sword and martial art skills. And along with the supernatural speed mentioned above, Hiei is incredibly agile, and has an excellent sense of balance, performing various flips and twists throughout the series with ease.