Logia

Logia (自然系 [ロギア], Shizenkei [Rogia], literally translated as Nature System) is a type of Devil Fruit. It is commonly characterized by giving its user the ability to turn into a natural element. Logia Devil Fruits are considered the most powerful of the three groups, as well as the rarest of the three types of Devil Fruit as a whole.

Effect
With these fruits, the user may actually become a natural element. They are neither completely human nor element in their default state. Logia users can turn completely into their element if they want to. This is often used for crossing great distances fast, or avoiding blows should their weakness be discovered. They have also shown the ability to use their powers to fight more indirectly, such as Crocodile's ability to suck the moisture out of anything.

Strengths
Even in their default states, Logia users are virtually invincible, taking no damage from physical attacks. For example, if their element is not solid, a blow can pass right through the user while they maintain the rest of their body, and can even hold onto objects at the same time. Even Aokiji's solid ice body will reform instantly if it is broken. If the user train their new powers, they can manipulate anything related to their element such as Crocodile's sand power giving him the ability to absorb moisture, or Enel's ability to use the heat from his lightning to reshape objects via melting. Logia users can tap unlimited amounts of their elements from their own bodies. The "extracted" element can be manipulated however the user wants.

Most Logia seem to have the ability to "fly". They either turn their whole body into their element, or just the lower half of the body. Smoker and Crocodile are two of the many capable of doing such a feat. Additionally, a Logia user's power over the element they control seems to afford them immunity to effects that they would normally be susceptible to.

However, the most dangerous aspect of a Logia-class Devil Fruit is its massive destructive powers, as most users shown so far are capable of creating great environmental hazards via manipulating their elements (such as Crocodile's sandstorms, Portgas D. Ace's firestorms, and Enel's thunderstorms), they can devastate wide range areas with extreme ease.

Weaknesses
The main method of causing harm to a Logia user (aside from exploiting the effects of the sea and Seastone) are natural weaknesses which, when exploited, can ultimately lower or negate a Logia user's power. For example, the electrically powered Enel can be hurt by insulating substances like rubber, which also makes the insulator immune to his lightning attacks. Another example is Crocodile, who, made of sand, can be struck if his body is dampened first.

The only other time a physical blow may hurt the user is when he or she is caught off guard, as this gives the user no time to mentally change into their elemental form. However, the powers of a Logia can be trained to counter this problem. An example was Crocodile, who honed his abilities to the point of being able to turn on his powers as a reflex to a blow.

Also, Logia users tend not to have any defensive abilities apart from their ability to turn into an element and let the attack pass through them. Because of this, when this ability is overcome, the Logia user usually has to dodge attacks. However, all of the users shown so far are seen to be quite resilient, and can get back up even after receiving some hard strikes.

"Haki" users have been seen to use their Haki against Logias to harm them. The details of this method is yet to be revealed. It should be noted that both Aokiji and Akainu have both been hit by Haki users with what would have been lethal attacks, yet they remained unaffected by the attacks. However, Akainu does mention that it is annoying to fight Haki users. Perhaps because it is a battle of two wills instead of simply being a physical attack.

Other information
Logia is the most powerful and rare of the three groups of Devil Fruit excluding of course, the only type of Zoan Devil Fruit that is the rarest and thus most mysterious, Mythical Zoan. Logia users cannot control their elements if it is in another state of matter. However, they may use their surroundings to generate it. These Devil Fruits are also not limited to the classical elements: fire, water, earth, and air, but includes physical states like smoke and sand. There are two types: tangible (something a person could hold like sand or ice) and intangible (something that could not be held like smoke or fire). Logia Devil Fruits can also be divided into two other types, forms of matter (smoke, sand, ice or lava) and forms of energy (electricity, light or fire). The only known Logia that does not fit into the latter method of categorization is Blackbeard's darkness. Furthermore, their ability to move out of harm's way by using their powers seems to serve as a defense-mechanism of sorts designed to save them from otherwise life-threatening attacks (i.e. getting cut in half). If not trained properly (like Crocodile has), it could be easily bypassed by non-lethal physical attacks. This was demonstrated by Luffy in Nanohana where he used a Gomu Gomu No Rocket to propel himself inside a restaurant, where he sent Smoker and Ace (both Logia-type users) flying. It appears that Logia users transformed in intangible elements such as light can still be pushed (as demonstrated when an explosion blasted Kizaru).

However, amongst the Logia fruits there seems to be an order of superiority. Akainu's magma overpowered Ace's fire. This left Ace in a state in which no medical aid could possibly hope to save him. This is an example of the danger of placing an inferior Logia against a superior one. Undoubtedly the Yami Yami no Mi, which has unique traits not found in other Logia fruit, has the potential to be dangerous to all Devil Fruit classes not just Logia. Something almost all Logia users seem to share (except for Marshall D. Teach), is they are not used to getting hit due to being so used to their virtual invincibility, and are visibly shaken when they are harmed, despite their resilience.

Many users of Logia fruits seem to have created their own form of personal transportation and use their abilities to power these devices. Among these are Ace's Striker, a small ship powered by his flame powers, Smoker's Blower Bike, a three wheeled bike powered by his smoke powers, Aokiji's Ao Chari, a bicycle which he uses to cross the sea, freezing a small line in the water to ride on and Enel's Ark: Maxim, a ship which uses gold as a conductor for Enel's electric ability to power the ship.

List of Known Logia Fruit

 * Moku Moku no Mi (English Versions: Smoke-Smoke Fruit/Plume-Plume Fruit): Element of smoke.
 * Mera Mera no Mi (English Versions: Flame-Flame Fruit/Flare-Flare Fruit): Element of fire.
 * Suna Suna no Mi (English Versions: Sand-Sand Fruit): Element of sand.
 * Goro Goro no Mi (English Versions: Rumble-Rumble Fruit): Element of electricity.
 * Hie Hie no Mi (English Versions: Chilly-Chilly Fruit): Element of ice.
 * Yami Yami no Mi (English Versions: Dark-Dark Fruit): Element of darkness.
 * Pika Pika no Mi (English Versions: Glint-Glint Fruit): Element of light.

Filler

 * Toro Toro no Mi: Element of some unknown liquid. (Movie 2)
 * Ame Ame no Mi: Element of semi-liquid and liquid candy syrup. (Movie 4)
 * Basa Basa no Mi: Element of paper. (Video Game)

Trivia

 * True to the rarity of the class, the Logia has by far the lowest known amount of users, including the unnamed one (i.e. Akainu's magma-based fruit). To go along with this idea, all shown Logia fruits seem to belong to incredibly powerful organisations (Navy, Whitebeard Pirates, Shichibukai and the God of Skypiea.)
 * The only female known to have consumed a Logia Devil Fruit is the non-canonical Honey Queen.