Phantom is one of Ayden's main Pokémon. Originally caught as a Gastly, though he eventually evolved into a Haunter, Ayden met Phantom in Agate Village, where he often tried to make people laugh, though he failed on many occassions, unintentionally scaring them instead.
Phantom is often regarded as an oddball of a Pokémon. Unlike other Gastly, Haunter and Genger, Phantom prefers to make people laugh rather than scare them. He would often appear behind people and make silly faces, but end up scaring them off with his sudden appearance and frightening grin. While Phantom often became depressed when he couldn't make people laugh, he didn't let that discourage him and kept trying.
As a Ghost-type Pokémon with Levitate, Phantom holds an immunity to Normal, Fighting and Ground-type attacks. In addition, he can easily phase himself through solid objects and disappear into shadows. Most of Phantom's moves focus on special attack and dealing damage from a distance, though he can induce status problems such as sleep, burn and confusion.
Phantom originally lived in the lower caves of Agate Village that led to the Relic Forest. Everyday he would try and try to make the people laugh at his funny faces, but only ended up scaring them away.
One day, a group of children from the Phenac City Pre-Gym arrived on a field trip to see the Relic Stone in the forest. When Phantom appeared to try and make them laugh with a funny face, he wound up scaring the entire class except for one student named Ayden. Phantom was initially stunned that he managed to make someone laugh and eventually followed her back to Phenac City. He surprised her when she got home and the two befriended each other, with Phantom becoming her fourth Pokémon.
Phantom's name is a reference to ghosts and his Ghost type.