i made a ghost type eeveelution because its october and i couldnt help myself. also this would never be part of the games because how i imagine the lore doesn't work with pokemon lore and it seems a bit dark to be in a pokemon game (yes im aware im saying this about a game franchise with balloons that kidnap children). shame

My idea for how this dude works is it evolves from Sylveon. Like it's essentially a zombified Sylveon. Specifically, a Sylveon will evolve into a Spectreon if it dies to a ghost-type Pokémon in battle. If Spectreon doesn't already have a trainer, then it'll find a graveyard to haunt until it finds one, at which point it is loyal to an extreme degree. Spectreon usually attaches itself to a specific trainer, so it's rare that a trainer catches one instead of just finding one and having it follow them around. Spectreon cannot die, and it has the ability to extend this immortality to its trainer. While it is intelligent, it isn't intelligent enough to realize the consequences of extending immortality to its trainer.

Its spine, ribs, and right hind leg bones are exposed as a result of partial decomposition (its coloration has also changed from its original white, pink, and blue as a result of partial decomposition), and its body is stitched together lest it falls apart. The bolts in its neck keep its head upright, and it has no mouth and thus communicates telepathically. It also has no need for food or water, and as a result of its immortality heals more quickly than other Pokémon.