The Six Paths Yin Power is a power wielded by Hamura and Hagoromo Ōtsutsuki, and later given to Sasuke Uchiha. It is represented by a dark-coloured, crescent moon-like palm seal (掌の印, shō no in) on the user's left hand.
As noted by Black Zetsu, there is a special resonance between the Six Paths Yin and Yang powers, allowing the wielders to sense each other's presence. When the Yin and Yang powers are used together, they can seal and transform their target into the core of the Six Paths — Chibaku Tensei technique. When Sasuke did so in conjunction with Naruto Uzumaki's Six Paths Yang Power, the palm seal on his left hand vanished, returning to Hagoromo's own left hand.