Tomoe

A tomoe or tomoye (archaic) (巴) is a Japanese abstract shape (i.e. a swirl) that resembles a comma or the usual form of magatama. Tomoe are usually seen in a design of three known as Mitsudomoe (三つ巴, lit. three tomoe).

They appear in the Sharingan eyes, and they also form the Cursed Seal of Heaven which Orochimaru put on Sasuke Uchiha and Anko Mitarashi.