Will Materialisation

The Will Materialisation is an ability that allows the user to manifest and materialise their "will" into a black substance or material for different purposes.

Kaguya Ōtsutsuki and Madara Uchiha
Kaguya Ōtsutsuki upon being sealed by her two sons formulated a plan that would result in her eventual resurrection. This led to the creation of the sentient-being Black Zetsu who, as an extension of her will, would enact this plan.

Kaguya and Madara were able to use a variation of this technique in a form of black rods. Madara was not only able to remotely manipulate the actions of those embedded with the rods, but also manipulate the receivers imbued with his will telekinetically.

Will in form of black rods also serves as chakra conductors and can be used with Six Paths Technique through Outer Path.

Similar cases
After her death, Karura's will inhabited her youngest son Gaara's sand, causing it to automatically protect him whenever he is in danger. Gaara's sand morphs to her appearance after this is revealed by his father.

Like its creator, Black Zetsu was also able to subtly influence the thoughts of others, or forcibly make them do his bidding by directly channeling his will through them.