Kyurem

Kyurem is a gray and blue, bipedal Pokémon of indefinable but seemingly draconic basis. Kyurem has a blue head and snout and has yellow eyes without pupils, a pair of pointed light bluish horns on its head, and a yellow crest on its skull that is bioluminescent. Three pointed teeth jut out the bottom of either side of its jaws, which are frozen shut by the ice covering its head. Its long, gray neck has lines running around its whole body, legs, arms, and tail. It has two arms, each with two claws, and each arm is joined by its oddly-shaped, blue ice wings. Each wing has two spikes which are bioluminescent. If its wings are broken, gray tendril-like appendages are revealed on Kyurem's back. The right side of its body seems to be damaged in some way, as the wing and horn on its head on that side are shorter; the right side of its head also has a spiked edge near its jaw hinge that is absent from its left. Its legs are somewhat slender and have three sharp ice-like claws on each enormous foot. Its tail opens up into three spikes arranged in an equidistant circle pointing backward, with center of this formation being hollow.

According to an old legend in Lacunosa Town, Kyurem is an extraterrestrial Pokémon that crash-landed on the planet inside on an icy meteor that may have been a Dragon Stone, creating the Giant Chasm. This legend describes Kyurem as hostile towards Pokémon and humans, due to the fact it supposedly devoured them if they were found outside of Lacunosa Town during the night. However, according to another old legend told by Drayden, Kyurem was created by the leftovers of the single powerful Dragon Pokémon commanded by the heroes of Truth and Ideals of Unova after it split up into Reshiram and Zekrom. Its true origin is unknown. Kyurem waits for a hero to fill in the missing parts of its body with truth or ideals.

Kyurem emits extremely cold air and generates powerful, freezing energy inside itself, but its body becomes frozen when the energy leaks out. Its latent power exceeds even that of Reshiram and Zekrom, but it is kept at bay by the extreme cold. To stabilize its cellular structure, Kyurem uses its ice powers to freeze its own body. It can use its tendril-like appendages to transform Reshiram and Zekrom back into their respective Dragon Stones and even absofuse with them while they're in that state. In Pokémon Adventures, much like Reshiram and Zekrom, Kyurem is somehow capable of flying despite its frozen wings. According to the Village of Dragons's Elder in Kyurem VS. The Sword of Justice (M15), Kyurem is considered one of the strongest Dragon-type Pokémon in the world, being powerful enough to cover Opelucid City and even the entire Unova region in ice. In the same movie, it is shown to be capable of speaking through telepathy. It loves Kyurem Treats made by Snacksworth, who once encountered it in the past.

Forms

Kyurem has two alternate forms: White Kyurem and Black Kyurem. These forms are created when it absofuses with Reshiram or Zekrom, respectively, and share many aspects of their designs with them, in addition to a shared belief in either truth or ideals depending on the current fusion. In Black and White 2, the absofusion process is shown as the tube appendages from Kyurem's wings forcing Reshiram or Zekrom back into their Dragon Stone forms, before the stone is absorbed by Kyurem to complete the transformation. In Kyurem VS. The Sword of Justice, Kyurem can also change into Black Kyurem or White Kyurem without fusing by channeling the powers of both Reshiram and Zekrom it has within itself.

Common aspects

Both forms of Kyurem have legs that are mostly the same as its normal form, except shorter and with a middle toe encased in ice. In addition, the fusion process with either Reshiram or Zekrom causes the ice covering its jaw to partially retreat, allowing its mouth to freely open. Kyurem's eyes gain black pupils while fused, as opposed to its base form having solid yellow eyes. The most notable aspect of the overall fusion process is the appearance of a new white or black turbine (depending on its fusion partner) that is attached to the hollow area of its tail and anchored to its body by the three tail spikes. Both forms add a third claw and extra size to Kyurem's previously near-vestigial arms, and have its original tube-wings shrink in size and reposition to become new shoulder attachments. In battle, the four tubes re-extend from their new positions on the back of the shoulders and connect to four corresponding holes in the tail turbine to activate Overdrive mode.

White Kyurem

White Kyurem resembles a hybrid version of itself and Reshiram, standing in Reshiram's upright stance as opposed to Black Kyurem and its base form's hunched posture. Its tail turbine's four holes, used to initiate Overdrive mode, are arranged horizontally in contrast to Black Kyurem. White Kyurem's torso is also slimmer, especially when compared to its counterpart, Black Kyurem. In a mirrored style to Black Kyurem, the right side of White Kyurem's body (Right-side head tuft and arm minus the inner elbow) is frozen. White Kyurem's arms have streaming, wing-like structures on its forearms; the lack of ice on the left arm exposes wrist and high arm cuffs styled like Reshiram's neckbands. In Overdrive mode, with the turbine actively generating Reshiram's fire, the ends of its right arm-wing and hair tuft glow a fiery red.

White Kyurem can use both the power of fire and ice due to fusing with Reshiram. Having foreseeing a future world of truth, it strives to protect said future for both humans and Pokémon.

Black Kyurem

Black Kyurem resembles a hybrid version of itself and Zekrom, with its stance still hunched forward like its base form but also more upright like Zekrom, with somewhat shorter legs. Zekrom's black wings appear on Kyurem's back between where its former tube-wings have become shoulder attachments. In a mirrored style to White Kyurem, the left side of Black Kyurem's torso (Left wing, horn, and most of the left arm save for the inner elbow) is covered in ice. The tail turbine's holes that are used to initiate Overdrive mode are arranged vertically, in contrast to White Kyurem. Kyurem's torso and arms gain significant bulk, and Zekrom's black skin and musculature replaces Kyurem's original gray skin on its arms and back of its neck. Black Kyurem has three sharp teeth on either side of its mouth, while White Kyurem only has two. In Overdrive mode, with the turbine actively generating Zekrom's electricity, parts of its right arm and the tip of the left horn turn blue with electricity.

Black Kyurem can use the power of both electricity and ice due to fusing with Zekrom. Having foreseen a future ideal world, it will fight to protect said future for both humans and Pokémon.

(Source: Bulbapedia)