Yami Yami no Mi

The Yami Yami no Mi, is a Logia type Devil Fruit that allows the user to become "darkness". "Yami" (闇) is the Japanese word for "darkness". In the Viz Manga, it is called the Dark-Dark Fruit. It originally belonged to Commander Thatch of Whitebeard's 4th division, but was stolen and eaten by Marshall D. Teach. This fruit is "unique" even for a Logia type.

Appearance
The Yami Yami no Mi is a purple fruit made up of many small teardrop shaped parts with swirl patterns, and spreading green leafage sprouting from the top. It closely resembles a pineapple or bunch of grapes in shape and appearance.

Strengths and Weaknesses
The first and foremost strength, as demonstrated by Blackbeard, is that it allows the user to control gravity. The gravity is visually demonstrated by a black smokelike liquid substance spreading out of the users body. As gravity sucks everything, including light, the fruit element is recognized as "darkness".

The darkness is a void that devours everything and crushes them. Due to this, the user can absorb physical matter and attacks of any type by sucking it into the darkness. The user can also use this ability to irresistibly pull the opponent to them, regardless in what state they're in.

The most unique and powerful advantage of the fruit, is that the user also has the ability to nullify the powers of other Devil Fruit users by simply touching them and draining them of their abilities. All powers from other Devil Fruit types, be it Paramecia, Zoan, and Logia, are affected by this.

Similar to a black hole, the user can suck things inside a vortex. Although it seems that it does not completely compress that what is sucked as a black hole would do, rather it seems to be some form of space where things are stored. Blackbeard sucked an entire city to it, and eventually regurgitated everything back out reduced to scraps. The guards of Impel Down that Blackbeard sucked survived, although they were heavily wounded and in shock.

The major weakness of this particular fruit, however, is that the darkness the user transforms into swallows up everything, including attacks. So unlike most Logia users, the user of the fruit is still vulnerable to attacks as they cannot turn into darkness in order to dodge them. If they fail to absorb the enemy's attack in time, the user can be hurt like any other normal human being or even more, as stated by Teach. This is especially dangerous against someone like Whitebeard, who even with his powers nullified, was considerably stronger than Teach.

In addition, while the ability to nullify Devil Fruit abilities is powerful, the user must actually touch and remain in contact with the victim for the affects to remain constant, meaning that if the victim separates from the user's physical touch, they quickly regain their Devil Fruit ability. Although, due to the fact that the user can control gravity, it is impossible to avoid contact. Furthermore, direct skin contact seems to be required to trigger the power-canceling affect, since Whitebeard was able to use his powers on Teach despite having his hand around his neck (via the beard) at the time, also the user need at least some amount of concentration on using it as shown when Luffy struck Blackbeard down and did not lose his Devil Fruit ability upon contact.

Other than that, the user is also affected by the standard Devil Fruit weaknesses.

Usage
The fruit's bestowed powers, as used by Teach, have been used so far for mostly combat purposes. He was able to defeat Ace in battle, his former commander, despite Ace possessing the Mera Mera no Mi.

The named techniques that are used by Teach that involve the Devil Fruit are as follows:


 * Black Hole (闇穴道 [ブラック･ホール], Yami Ana Michi [Burakku Hōru], literally translated as Black Hole Path): Blackbeard spreads his darkness over a large area and, much like a real black hole, swallows up anything he chooses. When swallowed it is subjected to a large amount of gravity and crushed, such as an entire village on the island of Banaro. During the Impel Down Arc, Teach has shown the ability to swallow up humans as well and crush them along with the debris. It could also be used to bind moving targets in place, leaving them open for subsequent attacks. Teach can also use Black Hole to create a harmless area of darkness on ground that negates entire devil fruits in range of darkness, as he completely nullified Whitebeard's devil fruit. This technique was first seen as it was demonstrated in front of Ace.


 * Liberation (解放 [リベレイション], Kaihō [Ribereishon]): Used following Black Hole. Blackbeard expels all of the destroyed remains of what his darkness has swallowed up at once. This is especially good at demonstrating his power. This was first seen being demonstrated before Ace. Though it is unseen as of yet, in the anime Teach foreshadowed this attack can possibly be used to launch cannon balls and swords like projectiles.


 * Kurouzu (闇水, Dark Vortex): Extending one arm towards his opponent, Blackbeard activates the gravity power of his darkness to pull them into his grasp. Blackbeard can then attack them with his massive strength. This move is particularly useful in conjunction with the Yami Yami no Mi's power-nullifying abilities, since the target could easily avoid it by fighting at a distance from Blackbeard, as Ace attempted. The name of the attack is also a pun on the English word "close". This was first seen being used on Ace in order to grab him.

Trivia

 * This is the only Logia-class Devil Fruit shown first as a fruit before its powers are demonstrated.
 * Darkness type is the first and only devil fruit that has an unique counter ability over entire other devil fruits in One Piece universe.
 * It's is yet to be confirmed that the Yami Yami no Mi indeed was the reason that Teach could steal the Gura Gura no Mi or if this process can be repeated more than once.