James's Yamask

James's Yamask (Japanese: コジロウのデスマス Kojirō's Desumasu) is the first Pokémon that James caught in the Unova region, and his tenth overall.

History
Yamask appeared before in a warehouse in Battling For The Love of Bug-Types!. suggested that they capture him to increase their strength. Jessie agreed and called out her to battle him, but James claimed he was hungry and he proceeded to feed him. Once he was full, he happily went into James's Poké Ball, the trio welcoming their newest addition with enthusiasm.

In Scare at the Litwick Mansion!, Yamask befriended a group of in a mansion that Team Rocket was temporarily using as a base. However, he was kidnapped by the Candle Pokémon in an apparent attempt to lure James, Jessie and Meowth into a trap. Yamask teamed up with Jessie's Woobat,, , and to defeat the Litwick and their  leader.

Yamask was used in A Restoration Confrontation! Part 1 to capture a that Dr. Zager had just resurrected, however it escaped after blowing a hole in the helicopter with. In the next episode, Yamask ambushed Ferris and the group with and battled to capture the Prototurtle Pokémon alongside Woobat. After Tirtouga evolved into and fled the scene, Yamask used his  to stop  and  from following. Yamask later battled Pikachu and, revealing his attack, as they tried to rescue the captured Carracosta before the time gate at Twist Mountain.

Sometime before An Epic Defense Force!, Yamask helped Team Rocket kidnap, who was living in hiding, by distracting Meloetta's protector, Ridley, with his Haze attack. In All for the Love of Meloetta!, Yamask helped uncover Meloetta while Team Rocket were pursuing it. Later in Meloetta and the Undersea Temple! he surrounded Ash and the others with Will-O-Wisp and then revealed Meloetta from its invisible state. Yamask continued to battle and Pansage while  pursued Ash who had then fled with Meloetta. Then in the next episode Yamask and Woobat used their combined attacks to launch Ash of the top of the ancient temple to prevent him from interfering with Operation Tempest. When Team Rocket were finally defeated, Yamask allowed them to retreat by concealing them all with Haze.

Yamask also helped to fight off Team Plasma's controlled Pokémon in What Lies Beyond Truth and Ideals!.

Yamask made his final appearance in The Dream Continues!, where he attacked Ash, and Alexa with Will-O-Wisp. Later in the episode, he was given away to Giovanni for Team Rocket's cause.

Personality and characteristics
Like many of James's Pokémon before him, Yamask is very friendly and is shown to have a great relationship with his Trainer. He is a very thankful Pokémon, as shown when he let James catch him after he was given some food. Unlike several of James's other Pokémon, such as, and , Yamask doesn't show any kind of special affection to James when coming out of his Poké Ball.

As seen in A Fishing Connoisseur in a Fishy Competition!, he can use his mask to deflect attacks, much like how Ash's Oshawott uses his scalchop. He can also, like Jessie's Seviper before him, use to shroud Team Rocket in a dark cloud of smoke to allow for a quick escape.

Trivia

 * Yamask is the first Pokémon to be officially owned by a main character.
 * This is the first Pokémon James has added to his party since in Two Degrees of Separation!, 212 episodes before. However, since Carnivine was actually obtained when James was still a child, this is his first capture in 259 episodes, with the capture of
 * Yamask is the only Pokémon caught by in Unova whose capture was on-screen.
 * Yamask is James's first Pokémon whose gender is confirmed.