Transcription Seal: Amaterasu

This is a technique that seals the technique Amaterasu within the Sharingan of another person. After being sealed within the person it is involuntarily activated when certain conditions are met. Itachi used this technique on his brother Sasuke Uchiha as a fail safe against Madara Uchiha should the two ever meet. Upon seeing Madara's Sharingan, Sasuke's eye took the form of Itachi's Mangekyō Sharingan and used Amaterasu on Madara, though it did not succeed in killing him. Itachi planted this seal in Sasuke when he put his two fingers on sasuke's forehead right before his death.