Haki

Haki is a mysterious power that allows the user to utilize their own spiritual energy for various purposes.

It can be used to sense people's spiritual energy and predict their actions, give the user a protective coating of spiritual energy, and, for a certain group of "chosen ones", overpower the willpower of others.

All living beings in the world are capable of learning Haki, however, most people do not notice it or fail to awaken it.

"“A manifestation of you’re willpower,to be as hard a armor.To have Extrasensory or future vision.To overpower people with your will,Yes that is Haki!”"

- -Raylord explaining Haki to Surge.

Overview
First seen when Eyeball Used Busoshoku Haki on Surge,It was use by Brycen,Lucas and Espada before it was fully explained In the C vs Surge fight at Loguetown seeing how C used Busoshoku Haki and Kenbunshou Haki he gave surge some info about Haki