"Obito claims to be Uchiha Madara, and long ago I did come across some information regarding Uchiha Madara." Itachi felt he should share this with Feitao; previously there hadn't been time, but now they needed to exchange intelligence.
Uchiha Madara. Surely no ninja in Konoha was unaware of that name. After all, he was the one who founded Konoha alongside the First Hokage, and a supreme powerhouse whose fame rivaled the God of Shinobi.
"Both he and his younger brother awakened the Mangekyo Sharingan, but later, due to the backlash, they gradually lost their sight. Rumor has it that he killed his younger brother to take his eyes, and only thus obtained ultimate power, ultimately fighting a decisive battle against Lord First at the Valley of the End and dying there."
Chapter 319