Dark Blood

Dark Blood (黒血, Kurochi) is a mythological substance that is known to give people the power of a "demon". If someone use this wildly power will end up suffering huge changes physically as the fact that some parts of the body are altered or even gain horns or wings. The assistance of this blood is simply assumptions because it hasn't been discovered if demons are real or just people's inventions. The first person to be revealed of supposedly have this blood is Ueda D. Katsu.

Usage
Dark Blood is considered a drug, and the main effect is the immediate transformation of another blood for black blood. There are only two ways to have this blood, the first and most used is to be injected with the blood which will change user immediately but can be easily rejected. The second and more difficult to find is born with his own black blood, both can be born with half or all the blood of the black body. With half of the blood, the user does not have any control over the powers and to show them it is necessary to be in danger of death. With all the blood at the beginning the user can't control but with practice easily release the blood outwards creating an impenetrable shield.

When someone uses the power of the blood, typically this person wins some kind of mark on the body, and when a controlled part of blood spreads through the body creating an indestructible mass that can easily change shape indeterminadamente. the first person to possess this power was Ueda D. Katsu and as such he showed able to use with every advantage the blood creating weapons, assas, and even in conjunction with the Busoshoku Haki.

Side Effects
The biggest side effect of blood is when someone injects in the body and is rejected, this causes instantaneous death since the original blood is completely destroyed. Another side effect is the fact that to control this great power requires a great willpower, lots of power and in some cases pure luck.