Naruto Cursed Seal -

Orochimaru developed the Cursed Seals by studying the transformation processes of Jūgo’s clan. Jūgo’s body naturally absorbs massive amounts of Natural Energy, causing uncontrollable, violent rages and physical mutations. Orochimaru synthesized this enzyme to brand his followers.

This is arguably the most famous seal in the series. Applied on the back of Sasuke's neck by Orochimaru during the Chūnin Exams, it played a pivotal role in Sasuke's descent into darkness. naruto cursed seal