More Info On Hiei
Hiei is a monster whose true origins are unknown. He is a master swordsman, and his strength and speed are incredible. However, these are hardly his most fearsome abilities. Typically kept concealed behind a bandanna on his forehead is the Jagan, a mysterious third eye that possesses magical properties. With it he can control weak-minded humans, send telepathic messages, and move objects telekinetically. Hiei is fiercely independent, and his raw ambition drives him to pursue his own agenda at all times. Although he generally cares little for human life, and views others as mere obstacles in the pursuit of his own goals, Hiei strictly adheres to his own unique code of honor. As such, he helps those who help him, and is fiercely loyal to those who have managed to earn his respect.
Hiei is a fire demon with a cold demanour. He was born into an ice demon clan as a child, and because they discovered that he was a fire demon, they gave him the boot. Hiei spent much of his time being a youkai delinquent and looking for his lost sister, Yukina the pretty blue-haired, demure, ice demon.

Hiei and Kurama are old friends and both came to the human world after stealing objects from the Spirit World. Kurama stole the mirror of utter dark and Hiei, a sword, "The Ghost Slayer", with a poisious blade that could turn any human into a demonic minion. Hiei had a Jagan (demon eye) implanted on his forhead so this is why he often wears a headband. He is also an expert swordsman.
Born in the land of ice maidens (the Floating Kingdom of Koorime; Ice Country of Makai), Hiei was considered to bring bad luck to the maidens for he produces fire. The maidens wanted him to die, and so they set of to a cliff, where they dropped the baby and wrapped him in straps with writings. Hina, Hiei's mother, begged them to spare her son's life, but no one listened. Ruri, Hina's friend, whispered to Hiei that he should survived, and tucked inside Hina's tear gem. She added that she will await his revenge.

He was found by a pack of thieves, and from then on, lived like them. When he became strong and heartless, the men who raised him couldn't take his attitude, and removed him from their group. Hiei was left alone and he continued fighting, until one time, he dropped the gem during a fight and it vanished in the water.
In order to find the gem and the land of the Koorime, Hiei approached Shigeru, the man who will give him his third sight, the Jagan. In exchange for Shigeru's effort, Hiei agreed never to tell Yukina that he is her twin and brother. He didn't want to anyway.
Now that he has the Jagan, Hiei found the land of the Koorime, and met Ruri, who did not notice that he was the Forbidden Child. He asked hr questions about the child, and she brought him to Hina's tomb, who was said to have committed suicide (or was forced?). She also told him that Yukina, his sister, went in search of her brother. Realizing that it was Hiei she was talking with, she cried and begged for his forgiveness, thinking that he will kill her. He did not, and he did not get revenge on the maidens. He simply left in search of Yukina, thinking that she was his responsibility, since she was his brother.
Hiei met Kurama in Ningenkai while he was was searching for Yukina. They fought each other, because they thought each one was an enemy. He got wounded in their fight, and it was Kurama who treated his wounds. In return, he helped Kurama rescue Maya, his friend and girlfriend at that time, from a man-eating youkai. They became friends after that.

When they got involved in a robbery, in which they stole the Rei kai gems, they met Yusuke, the Rei kai Tantei (Spirit World Detective). Yusuke was able to defeat Hiei with the help of Kurama (who was returning a favor) and the two of them (Hiei and Kurama), were ordered to serve as a tantei in Rei kai. They became friends, although Hiei doesn't socialize much, and went on to missions with Yusuke.

Some of his techniques are
*Speed - Hiei is quicker than the human eye. It appears that he's phasing but he's simply moving so quickly that you can only catch a residual picture here and there.

*Jagan - Hiei's third eye gives him the power to see great distances as well as control people.
*Fire - obviously he can do some pretty tricks with fire being a fire demon. Including the following;

*The Jaou Ensatsu Rengoku Shou (Swift Demon Purgatory wound -geh, my translation is weird!) is his multiple-hit Ki punch attack Hiei uses, with fire forming around his fists, he proceeds to pummel his opponent rapidly.

*The Jaou Ensatsu Ken - Hiei summons black fire in the form of a sword around his right fist. He dosn't like to use this though, because it looks like Kuwabara's Rei Ken and of course, he thinks that anything relating to Kuwabara is obnoxious and clumsy.

*The Jaou Ensatsu Koku Ryu Ha is the most powerful of Hiei's attacks. Literally, The Flying Black Dragon Wave of Destruction, The Koku Ryu Ha, when dormant, is a black dragon tattoo on Hiei's right forearm. When he calls on it, it manifests its'self from the same arm as dragon of black fire, that destroys everything in its path.. Only Mukuro, and Bui, were able to stand up against this attack. Because they did so, the Kokuryuhaa came back at Hiei and he was possessed by it.

*Katana (Sword) - this is the weapon he uses most of the time, using it to kill whoever gets in his way.

*Ensatsu-Koku-Ryu-Ha (Fire-Killing-Black-Dragon-Wave) - this is known as the Black Dragon Spirit Technique, wherein he manipulates a black dragon from Makai and uses it to defeat his opponent. This is his best technique and is most used after the katana. It takes a huge amount of his ki, leaving him deflated afterwards. This technique once scorched his arm after his fight at the Ankoku Bujutsukai (Black Martial Arts Tournament).

*Jaou-Ensatsu-Ken (Evil-King-Fire-Killing-Ken) - also known as the Black Fire Sword, it makes use of fire and youki to strengthen his sword.

*Ensatsu-Rengoku-Shou (Fire-Killing-Purgatory-Scorching) - fire appears in his fist and he does a series of fast punches.