James' Yamask is a Pokémon James caught in BW025 while he, along with Jessie and Meowth, were searching for their boss Giovanni after he disbanded Team Rocket. Its battle strength can't be gauged very well as it makes only intermittent appearances.
While searching for their
Boss, James caught Yamask after feeding it, it then happily accepted becoming James' Pokémon.
BW029, three devious Litwick tricked Yamask and kidnapped it along with Meowth, Iris' Axew, and Ash's Pikachu but the Litwick and their Lampent leader were defeated by them.
BW030, it teamed up with Jessie's Woobat to take down and capture Iris' Axew and Amy's Druddigon but was defeated by Druddigon's Draco Meteor.
James' Yamask is the first Ghost Pokémon owned by a main character.
Unlike James' past Pokemon, Victreebel, Cacnea, and Carnivine, Yamask does not show any kind of affection when it is sent out.
Similar to how Ash's Oshawott can use its Scalchop as a shield, James' Yamask can use its mask as a shield to defend its ally in battle.
Simillar to Jessie's Seviper, Yamask can use Haze in order to shroud Team Rocket in a cloud in order to prevent their cover from being blown.