well i guess u aint seen any Naruto then...
Its called A cursed seal (bakka).
its a strange power granted by Orochimaru to all his minions.
it amplifies a ninja's chakra (energy) and slowly consums the persons individuality untill they are a mindless clone.
it has 2 stages as far as i am aware, level 1 which is a partial covering of the face and body with black swirly things.
level 2 changes your skin colour and depending on the type of seal you have, different powers emerge, such as Giant hands on your shoulders or extra eyes etc etc.
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