First, let’s start with the 3 types of devil fruits:
- Paramecia: This devil fruit covers the widest array of abilities and can be quite random, ranging from changing the substance of a person’s body(Luffy being the prime example being made of rubber). It can offer new abilities such as Whitebeard’s ability allowing him to create earthquakes. Or change how you can control your body, such as Buggy who can split his body into many different pieces. This class offers endless possibilities for new powers.
- Logia: This allows the user to change their body into the substance or element of their devil fruit. Unlike Luffy’s devil fruit this allows them to be Intangible and incapable of being hit by normal means of punches or kicks. Ace could turn into fire, Akainu into lava, Smoker into smoke, Crocodile into the sand, Enel into lightning, and Kizaru can turn into light. They carry the same attributes as their devil fruit. For example, Enel can travel at the speed of lightning and Kizaru at the speed of light. Enel can use his abilities to hear using electromagnetic waves allowing him to hear for hundreds of miles.
- Zoan: This grants the abilities of certain animals, there are multiple subclasses of this type(Mythical Zoan for example). This fruit allows its user to change into a part animal or take on the attributes of that animal. Claws, fangs, wings, etc, gain increased speed, strength, durability, or regeneration relative to that animal.
Haki also falls into 3 categories:
- Armament haki: This allows the user to use their “spirit” and manifest it as a black substance that can cover their body or weapons that they use(swords etc) the strength of the armament is relative to the skill of the user, it could be as strong as concrete or as strong as steel, or hundred of thousands of times stronger then steel solely depending on the user’s ability, what’s special about Armament haki is it allows you to hit Logias even after they’ve transformed into the material of their devil fruit. This ability is used specifically to counter Logias.
- The next step above this is Advanced Armament haki which allows them to use their spiritual energy to damage their target without making contact. This ability also can insert the spirit energy into the object and expand creating an “explosive force” causing massive damage. If you were to punch someone using this ability and they didn’t use haki internally on their organs or have extreme regenerative abilities or extreme durability, their insides would explode. This ability is rather newly introduced so the specific are hazy and Are subject to inference.
- Observation haki: This allows you to sense your surroundings increasing all of your senses. Allowing you to sense opponents who are even out of sight, if someone sneaks behind you, allowing you to sense even stealth. It’s useful in combat because you then notice and observe every detail of your opponent that you couldn’t sense before allowing you to predict and much more easily counter their moves. Above this is Advanced Observation haki which allows the user to see into the future, the distance into the future depends on the skill of the user. The most ability that’s been shown is by Katakuri and Luffy who were capable of seeing only several seconds into the future.
- Conquerors haki: Unlike the previous haki this is the only haki that cannot be attained by training. You are born with this innately and it allows you to insert your will over other people, if you have a weak will they can forcibly make you pass out. It can also be used to tame wild animals instantly.
Devil fruits and Haki can be used together to enhance and reshape abilities, Luffy being a prime example with his Gear 4, it’s up to the user’s imagination.