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* Shikai: The Shikai form of Zangetsu looks like an oversized elegant cleaver than a formal "katana". He has no crossguard and no proper hilt; what Ichigo holds is the cloth-wrapped tang. The sword is as tall as Ichigo is, 1.75 meters, and has a black blade with a silver edge. The cloth wrapping on the tang seems to react to Ichigo's will, changing length at a thought or twining about the blade in an impromptu sheath. When in combat, the cloth falls away when necessary, shrinking back to a manageable size. The cloth can also be used to swing the weapon like a flail and toss it at opponents, but this is rarely done. The cloth also can be done to wrap up wounds, as Ichigo does during his fight with Ikkaku Madarame, but this is also done rarely. Unlike most zanpakutō, which can be sealed into their original form, Zangetsu is always in its Shikai form. Yoruichi Shihōin has stated that his zanpakutō is a full-time released form type, implying that it is simply a type of zanpakutō that, once in Shikai form, remains in said state.

Shikai Special Ability: Zangetsu's special ability is the Getsuga Tenshō (月牙天衝, Moon Fang Heaven-Piercer; "Piercer of Heaven" in the English anime), which fires concentrated energy blasts from the tip of the blade in the shape of a crescent moon or in a shape of a wave. Ichigo uses this ability without knowing its name several times, but masters the technique later on when he discovers its name. As stated by Zangetsu in the anime, knowing the name of an attack increases its power greater than not knowing its name. The Getsuga Tenshō is a powerful technique with great force. While it is currently the only attack Ichigo knows from Zangetsu, Ichigo has used this technique in several different manners, such as striking the ground to create an omnidirectional blast to knock away incoming attacks.

Zangetsu's Bankai form: Tensa Zangetsu

* Bankai: Tensa Zangetsu (天鎖斬月, Heavenly Chain Moon Cutter or Heavenly Chain Cutting Moon): It is considered completely out of the ordinary for any zanpakutō. Unlike most Bankai forms, which usually create some sort of massive creature or effect, Ichigo's Bankai actually shrinks his sword down to a daitō (Japanese long sword) with a black blade, the crossguard is Four prongs bent out to form the shape of the manji (which is the kanji for "ban," meaning "full"). Instead of the cloth his Shikai form had, a short length of chain with a broken link at the end dangles from the base of the hilt. In addition to his sword, Ichigo's robe is replaced with a long-sleeved, ankle-length black coat with red lining that is closed at his chest, then left to flare out into ragged ends, much like that of Zangetsu himself. Ichigo's initial inexperience with controlling his Bankai led to a serious drawback; the force of his compressed spiritual power caused all of his bones to crack, as stated by his inner Hollow, gradually decreasing his speed and power over time. This drawback has not been mentioned since its introduction, so it has (presumably) been overcome.

Bankai Special Ability: Zangetsu's special ability remains Getsuga Tenshō. When used with Zangetsu's Bankai, these potent blasts are black with a red outline and their path can be controlled, with explosively augmented power and speed. During Byakuya Kuchiki's fight with Ichigo, he refers to this attack as a "Kuroi Getsuga" (黒月牙; "Black Moon Fang"). This term simply refers to the darkened color of the attack, not its actual name. When used with his Bankai and Hollow mask in combination, Ichigo's tremendous speed allows him to move faster than the Getsuga Tenshō itself, allowing him to fire multiple blasts from different directions. The Kuroi Getsuga was first displayed by Ichigo's inner Hollow, and initially carried the risk of causing his inner Hollow to surface if used too much. With Ichigo's later control over his inner Hollow, this is no longer a problem. Ichigo is also capable of utilizing Getsuga Tenshō to augment blade swings, as seen in the fight with Byakuya Kuchiki, and the manifestation of Ichigo's inner Hollow. In fact it has come to a point where it literally just comes out of Ichigo's body, replacing his blue aura. It should also be noted that ever since Ichigo mastered his Vizard form, he produces a black aura that rages in the form of the black Getsuga Tenshō that surrounds him as he initiates Bankai, rather than a white aura that shoots high into the sky. During his second fight with Ulquiorra, Ichigo retained his Getsuga Tenshō in his blade, giving each attack the power of Getsuga.

* Physical Enhancement: As explained by Byakuya Kuchiki, Ichigo's Bankai is a compression of his remarkable power, rather than a vast expansion as other Bankai are. This vastly compressed power enables to reach levels of physical and spiritual prowess most Shinigami would have their bodies give out at and cannot handle. It allows Ichigo to move at very high speeds exceeding those of flash steps, and gives him matching agility and reflexes, possibly equaling if not, surpassing Yoruichi's speed, along with allowing him to use his natural strength to its limits as shown from how effortlessly he blocked a punch from Yammy, an Espada known primarily for his immense strength. The Shunpo's speeds are also enhanced in this state, allowing him to use Flash Steps at a speed much greater than Byakuya Kuchiki's. In addition, his already immense spiritual energy has grandly and explosively increased, and now has a deep black spiritual energy with a crimson outline.

* Enhanced Bankai Duration: Furthermore, the fact that all of his energy is "compressed" means that usage of his Bankai doesn't expel as much spiritual power as other Bankai from the point of activation; thus allowing him to use Tensa Zangetsu at a much longer duration than any other Bankai users of his level. With enough usage and acquired height, Ichigo can even appear as though he is flying.

Source: Wikia