Kyurem

"Do you think you're worthy of battling me?"

- Kyurem questioning Keldeo's challenge.

Kyurem is a legendary dual-type Dragon/Ice Pokemon introduced in Pokemon Black 2 and ''Pokemon White 2. In most of its appearances, it is portrayed as a villain. ''

The Legend of Kyurem
Kyurem is an extraterrestrial Pokémon. However, one resides in the Giant Chasm in the Unova region after it apparently fell from a meteor. An old legend in Lacunosa Town describing Kyurem claims that it would take people and Pokémon away from the town and eat them. It is unknown how much credence there is to this story, however.

Black/White 2
The antagonists of the games, Team Plasma, controls Kyurem from their aerodynamic base, using its power to freeze Opelucid City. Ghetsis, and several Grunts claim that they intend to freeze all of Unova with Kyurem's power. Near the end of the main adventure, Ghetsis takes personal control over Kyurem and makes it do battle with the player, but not before ordering it to either kill or simply freeze the player.

After the player defeats Ghetsis, the Elite Four, and captures or beats either Zekrom or Reshiram, the player can go back to where Kyurem resides and either make it faint or capture it. If the player chose to capture Zekrom or Reshiram, they can be fused with Kyurem, using the DNA Splicers, to form either Black Kyurem or White Kyurem.

Kyurem vs. the Sword of Justice
In the movie, Kyurem lives in Full Court, an abandoned mining complex inside a mountain. It lives in seclusion and rarely interacts with the outside world. Kyurem is considered the strongest Dragon-type Pokémon in the world, having been born at the same time as Reshiram and Zekrom. It can harness the powers of both Reshiram and Zekrom at will, allowing it to transform into White Kyurem and Black Kyurem.

Kyurem's solitude is interrupted when another Pokemon, Keldeo, challenges the Boundary Pokemon to a battle in the mine. At first, Kyurem seems to be uninterested in the fight, asking Keldeo if he believed he is worthy enough to fight a creature as powerful as Kyurem. Keldeo manages to get the Dragon's attention when he claims to be a Sword of Justice, which is actually a lie. Kyurem accepts Keldeo's challenge, and creats an arena on a platform outlined by icy pillars. Since Keldeo lied about being a Sword of Justice, he wasn't ready or strong enough to fight Kyurem. Unsurprisingly, Kyurem easily overpowers Keldeo, and even manages to break his horn off in the process.

During their battle, the real Swords of Justice, Cobalion, Terrakion and Virizio entered Full Court and attempted to call off the fight before Kyurem eradicated Keldeo, only for the Dragon to freeze them solid to prevent them from interfering with the battle further. Keldeo succumbed to his fear of Kyurem and fled. This angered Kyurem, and made it relentlessly pursue Keldeo in order to finish their battle. Its search leads it to find an almost unconscious Keldeo on a train, where Ash, Iris, and Cilan were attempting to help Keldeo. Kyurem was forced to jump off the train when it entered a tunnel.

Eventually, Kyurem arrives in Roshan City with a small army of Cryogonal (his 'friends' according to Cilan) where it changes into White Kyurem and continues pursuing Keldeo. After finding the group and getting attacked by Pikachu, Kyurem again changes, this time into Black Kyurem, and flies up to a signal tower while his Cryogonal continue the chase. Keldeo's newfound friends try to lead Kyurem away from him so he can save the Swords of Justice back at Full Court. The first attempt is when it believe Keldeo is in a blimp, but when Kyurem sees it is only Iris and her Axew, the Dragon angrily froze the propellers, making the dirigible fall. Next, it brought an old train engine to a stop with ice, thinking it contained Keldeo; but after discovering only Cilan and his Pokemon within, it flew off and transformed back into White Kyurem, heading back to Full Court.

Kyurem arrives back in Full Court minutes before its foe and remakes the arena from earlier. Kyurem then noticed Ash and his Pokemon attempting to free the Swords of Justice. Kyurem was angered, not because of what they were doing, but because a human had entered its home and realm. It attmpted to atack them, but Keldeo deflected it. Keldeo then admitted to Kyurem that it lied about being a Sword of Justice, but the Boundary Pokemon revealed it knew that Keldeo was lying from the start. Kyurem then remade the ice arena from earlier and demand they end their battle.

After gathering the courage to face Kyurem again, Keldeo shifts into his Resolute Form and proceeds with his battle with Kyurem. Like the first round, Kyurem initially overpowers Keldeo with ease. Eventually Keldeo's horn regrows as he shifts into his Resolute Form, ending up longer than before and glowing, similar to a real Sword of Justice. This makes the battle more even-sided for a while, but Kyurem again gains the upperhand by freezing Keldeo solid, seemingly ending the fight. However, Keldeo's newfound power and confidence allows him to break free, earning him the move Secret Sword. With it, he landed a direct hit on Kyurem, who became pleased by the turns of events and witnessing Keldeo's true strength that made him a match for the Dragon's power. Kyurem then attacked at full strength by unleashing another attack, to which Keldeo deflected, but caused the strike to head straight for Ash, his friends, and the now freed Swords of Justice. Rather than let them be hurt, Keldeo jumps right in front of the attack, taking the brunt. This causes him to fall back into the arena and come dangerously close to losing consciousness again. Kyurem then pins him to the ground by placing his foot on Keldeo's regrown horn, and Keldeo admits defeat.

Rather than finishing the battle, Kyurem removes its foot from Keldeo's horn and transforms back into its normal form. The Dragon verbalizes its surprise that Keldeo chose to protect his friends rather than pursue victory, therefore earning Kyurem's respect. Kyurem then tells Keldeo that the Colt Pokemon has "a fine Sword" before lumbering off to return to its solitude. The entire mining complex soon begins shaking and collapsing due to the battle from earlier. Keldeo and all its companions make a break for the outside, but Kyurem simply looks up at its crumbling home and changed into White Kyurem to simply freeze the collapsing pieces into place, coating them in a thick blanket of ice. Ash and company let out impressed statements about Kyurem's "castle of ice" as it lumbers off back into its home.

Pokemon Mystery Dungeon: Gates To Infinity
Kyurem makes an appearance as the secondary antagonist in the 3DS game, Pokemon Mystery Dungeon: Gates to Infinity, and is referred to as male.

He has forseen the future that shows the destruction of the Pokemon world being caused by a lifeform called the Bittercold. Kyurem, seeing that the Pokemon of the world have become too hostile and thinking that there was no solution, made it his mission to protect that future by serving the Bittercold so it can destroy the world and end all misery.