The Uchiha clan were most feared for their powerful Sharingan, a kekkei genkaiwhich gives them the ability to see the "colours" of chakra, allowing them to analyse and copy their opponent's skills, along with a number of other abilities. Only a select few members of the Uchiha clan manifested the Sharingan. Due to their natural affinity for battle, and their proficiency with ocular genjutsu, many ninja considered it more tactically favourable to flee rather than face an Uchiha shinobi in one-on-one combat. Among the techniques granted by the Sharingan, the Izanagi and Izanamiare deemed to be forbidden, due to their effect of rendering the user blind in exchange for creating genjutsu capable of escaping death or trapping the opponent without failure. Though the clan was feared for their Sharingan, the eyes have also been transplanted into various characters outside the clan.