In BW026, Yamask befriended a group of Litwick in a mansion that Team Rocket was using as a base. However, it 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, Ash's Oshawott, Ash's Pikachu, and Cilan's Dwebble to defeat the Litwick and their Lampent leader.
Like many of James's Pokémon before it, Yamask is very friendly and is shown to already have a great relationship with its Trainer. It is a very thankful Pokémon as shown when it willingly entered James's Poké Ball after it was given a little food. Also, unlike most of James's other Pokémon, such as his Cacnea and Carnivine, Yamask doesn't show any kind of special affection to him when coming out of its Poké Ball.
As seen in BW037, it can use its mask to deflect attacks similar to how Oshawott uses his scalchop. It can also, like Jessie's Seviper, use Haze to shroud Team Rocket in a dark cloud of smoke to allow for a quick getaway.
A † shows that the move was used recently, unless all moves fit this case or there are fewer than five known moves.
Trivia
Yamask is the first Ghost-type Pokémon to be officially owned by a main character.
This is the first Pokémon James has added to his party since Carnivine in Two Degrees of Separation!, 210 episodes before. Since Carnivine was actually obtained when James was still a child, this is his first capture in 259 episodes.
Related articles
For more information on this Pokémon's species, see Yamask.