Haki

Haki is a power that allows the user to utilize their own spiritual energy for various purposes. Haki Books, which teach you forms of haki spawns every 30 minutes and despawns at 15. You can also buy a haki book from Doflamingo.

Busoshoku Haki
Busoshoku Haki (more known as Armament Haki) allows the user to coat the Haki in any body area to make it more durable. It can be used for defense or offense. Busoshoku haki also extends to your weapons.

Kenbunshoku Haki
Kenbunshoku Haki or Observation Haki gives you the ability to see future movements. Kenbunshoku Haki even works on bosses. when you press K on your keyboard you will activate it for a short time (roughly 11 seconds)