Haki (known as Ryuo in Wano Country) is an energy that all living organisms have. It can be embedded into objects by said Haki users have. However, not many characters in Paradise are aware of its existence or know how to use it.

There are three kinds of Haki. Conqueror's Haki, Armament Haki, and Observation Haki.

Conqueror 's Haki

Conqueror's Haki (Haoshoku Haki), known by a few as Supreme King's Haki, is the rarest of the three, only found in one of every 100 million individuals in the world.

It grants the ability to project one's willpower in certain radius to overpower others. Said radius and how much it can overpower others depends on the user's willpower and haki strength. If the difference between a user and their opponent is great, an opponent can faint. If two users' Conqueror's Haki come in come in contact, the impact creates bolts of colored lightning and double the reverberation.

Armament Haki

Armament Haki (Busoshoku Haki) is the most common of the three, an emission of a iron-strong coat on whatever the user is in contact with. A large concentration of this haki turns incredibly dark and close to black and its strength depends on the user's haki strength. If it even appears is up to the user expertise. It is able to come in contact with creatures, even through their Devil Fruit ability. This includes Logia-type Devil Fruit abilities.

A few characters use the surface of this haki's friction to create fire that doesn't penetrate the surface and burn the user.

Observation Haki

Observation Haki (Kenbunshoku Haki) is used to detect presences and their emotions in a specific radius of its user, despite being in their line of vision or not. This radius depends on the haki's strength. If said strength is high enough, the user may even be able to see moments in the near future.