The Yuki Yuki no Mi is a Logia-typeDevil Fruit that allows the user to create, control, and transform into the element of "snow" at will, turning the user into a Snow Human (雪人間,Yuki Ningen?). The fruit was eaten by Monet, but with her death has returned to circulation.
This fruit's major strength is that it allows the user to turn themselves into snow. Monet had an extreme level of resistance, if not outright immunity, towards cold, due to her Devil Fruit's element, much like Aokiji's Hie Hie no Mi powers. While the two Devil Fruits have similar abilities, the Hie Hie no Mi is superior to the Yuki Yuki no Mi. Two major differences in the fruit's abilities are that Monet's intangibility as snow was not always a solid form since she was able to choose to compress the snow, and that she couldn't directly freeze her target solid.
As a Logia, Monet could let physical attacks pass through her without injury and could only get wounded with the use of Busoshoku Haki, Seastone and heat. Her attacks could also be stopped if her body were broken apart before she could execute her attacks. She also has a weakness to heat, as shown when Nami used her Clima Tact's Heat Egg to damage her wing. Furthermore, she could also lose control of her body's transformations if she became mentally unstable, as shown when Zoro cut her in half non-lethally and the resulting fear and anxiety after she thought she was going to die. Other than that, she was also vulnerable to other standard Devil Fruit weaknesses.
As a Logia, Monet could turn herself into snow to avoid attacks by letting them pass through her, or by floating around attacks. She could also manipulate the density of the snow to form solid snow barriers. These barriers are extremely hard, making it difficult to destroy them, but she could easily pass through her snow barriers. She also had the ability to weaken someone and make them lose consciousness by hugging them, using her cold body to sap their own body heat. By transforming into snow she could secretly hide in snowstorms, as seen when she followed Trafalgar Law through the Ice Lands without being noticed.
She could also release a massive snowstorm to take advantage of the cold to weaken her opponents in a similar way. She also used her powers to change the battlefield into a snowfield so she could dive into the snow from her snowstorm to hide, move, trap and attack her enemies quicker.
Kamakura (カマクラ,Kamakura?, literally meaning "Snow Hut"): Monet forms a barrier of snow around a nearby person or object. The barrier is quite strong as it took Luffy several Haki-imbued punches while in Gear Second to break it. It was first used to protect Caesar from Luffy's surprise attack. A "kamakura" is a snow hut. In the Viz Manga, the move is known as Igloo.
Kamakura Jussoshi (カマクラ十草紙,Kamakura Jussōshi?, literally meaning "Ten Layers Snow Hut"): Monet creates a snow hut with ten overlapping layers of Kamakura, which is obviously much stronger than a single-layered one. It was first used to trap Luffy, stalling him to allow more time for Caesar to escape. In the Viz Manga, this move is known as Ten-Layer Igloo.
Yuki Gaki (雪垣,Yuki Gaki?, literally meaning "Snow Fence"): Monet creates a solid snow wall. It can be used to block a doorway, as she did to stop Nami, Robin and Chopper from chasing after the giant children. It can, however, be destroyed by a strong swordsman like Zoro, who can slice steel. In the Viz Manga, this move is known as Snow Wall and in the Funimation subs, this move is known as Snow Fence.
Mannen Yuki (万年雪,Man'nen Yuki?, literally meaning "Perpetual Snow"): Monet completely turns to snow and then proceeds to surround an opponent's body with the snow, weakening and immobilizing them with the severe cold she exudes. While the enemy cannot move, Monet then transforms into a large snow monster with long fangs made of solidified snow, which can easily rip through flesh and bone, although the enemy does not bleed due to the wound freezing from the cold bite. However, if the victim manages to grab a hold of Monet while she's biting them, as shown by Tashigi when fighting her, she will not be able to tear off the afflicted body part, though she can still injure them further by biting harder. It was used against Nami and Chopper but stopped by Robin. It was later used on a G-5 Marine, taking a chunk out of his shoulder. In the Viz Manga, this move is known as Permafrost and in the Funimation subs, this move is known as Perpetual Snow.
Tabira Yuki (たびら雪,Tabira Yuki?, literally meaning "Sword Snow"): Monet freezes the feathers on her wings, transforming them into sharpened, solid snow-blades capable of clashing with Zoro's swords. In the Viz Manga, this move is known as Snow Sheet and in the Funimation subs, this move is known as Snow Sword.
Hada Gatana (肌刀,Hada Gatana?, literally meaning "Skin Sword"): After Tabira Yuki, Monet uses her wing to attack her enemy, slashing with it as if it were a sword. In the Viz Manga, this move is known as Skin Blade.
Yuki Rabi (雪兎,Yuki Rabi?, literally meaning "Snow Rabbit"): Monet swings her wing to release numerous solid hardened snowballs with small rabbit-like ears, whiskers, and eyes. It was used against Tashigi but, since she dodged it with Soru, the offensive properties of the attack are unknown. In the Viz manga and FUNimation subs, this is called Snow Rabbit.
Fubuki (雪嵐,Fubuki?, literally meaning "Snow Storm"): Monet releases a stream of snow from her lips that quickly surrounds an enemy and traps them within a blizzard. It is very similar to Crocodile's Sables but it does not send people flying. This was first used against Tashigi.
Canonically, this was the first Logia fruit that was eaten by a female character.
Fitting in with the mythical creatures theme on Punk Hazard, this Devil Fruit made Monet similar to a Yuki-onna, a Japanese spirit depicted as a woman that lures travelers into blizzards and freezes them to death.
Monet's description as a Yuki-onna in the manga also follows the trend of Devil Fruit users being described as a [something] human, depending on the nature of their ability, although she was separately called a Snow Human in the anime.
In the manga, Nami refers Monet as a Snow Woman (雪女,Yuki-Onna?) based on her ability, instead of Monet referring herself as a Snow Human.