Phantom

John's Spiritomb (Jon's Mikaruge), nicknamed Phantom, is the ninth Pokemon obtained by John in Sinnoh. John initially met this shiny Spiritomb on Route 102, where she ambushed and attacked him, laying a 'Curse' on him. After a series of unfortunate events begin to befall on him, he begins to believe that the curse is actually following him. When he encounters the Spiritomb again after surviving a near-death experience at Spear Pillar, he believes that if he catches her, the curse will die. He catches Spiritomb, and it seems that the curse goes away as he gradually makes friends with her.

In the wild
Freed by a bunch of reckless children from its place in the Forbidden Tower, this shiny Spiritomb was in a grumpy mood after being awakened from her sleep. She stumbled upon John training that day and attacked him, laying a curse on him. She fled the scene and met up with him again at Spear Pillar after surviving the shipwreck and defeating Team Galactic, where she attacked him again.

Having been fed up with her curse, John figured that maybe if he caught her and befriended her, the curse would die off. So he battled and caught Spiritomb.

With John
After catching Spiritomb (whom he nicknamed 'Phantom'), John was unable to train her properly for a while because she kept attacking him. Finally gaining her trust shortly before challenging the Pokemon League with help from Professor Rowan, Phantom became a vital asset for John's team, especially in his League battles against Lucian and Cynthia.

After the league battles, John decided to start off in a new region with a clean slate. So he left Phantom, alonside his other party Pokemon, at his home in Twinleaf Town before setting off with his baby Mijumaru, nicknamed Blue Moon, to the Isshu region with his friends.