My entry for this contest.

HALLOWSTUME
Costume Pokemon
Type: Fairy/-
Ability: Unaware/ Frisk/ HA: Shadow Tag
Height: 60cm
Weight: 12 kg
Signature move: Identification*
Dex entry: At night it can change its costume depending to the place where it is. You can see groups of Hallowstume wander around the towns looking for sweets and candies.
Hallowstume's costumes*:
Witch costume (towns and marshes)
Vampire costume (caves and dark places)
Pumpkin costume (woods and grasslands)
Skeleton costume (mountains and deserts)
*Identification: Type (depends to the Hallowstume's costume): Psychic (Witch costume)/ Flying (Vampire costume)/ Grass (Pumpkin costume)/ Ground (Skeleton costume); Category: Special; PP: 15; Power: 70; Accuracy: 90%. When Hallowstume evolves, this move turns automatically, depending to the evolution, in Starry Touch*, Bloody Wind*, Gourd Bomb*, Dead land*.
*Hallowstume's costumes: it works like Burmy's cloaks.

WITCHSTUME
Evolves from Hallowstume witch costume at level 37.
Costume Pokemon
Type: Fairy/ Psychic
Ability: Unaware/ Magician/ HA: Shadow Tag
Height: 1.50m
Weight: 36 kg
Signature move: Starry Touch*
Dex entry: It evolves when it identifies completely with the witch costume. Witchstume have the ability to do anything waving the magic wand.
*Starry Touch: Type: Psychic; Category: Special; PP: 15; Power: 85; Accuracy: 95%. 30% chances to confuse the target.

VAMPSTUME
Evolves from Hallowstume vampire costume at level 37.
Costume Pokemon
Type: Fairy/ Flying
Ability: Unaware/ Insomnia/ HA: Shadow Tag
Height: 1.70m
Weight: 31 kg
Signature move: Bloody Wind*
Dex entry: It evolves when it identifies completely with the vampire costume. Vampstume have the ability to fly perfectly in darkness.
*Bloody Wind: Type: Flying; Category: Special; PP: 15; Power: 85; Accuracy: 95%. 30% chances to confuse the target.

PUMPSTUME
Evolves from Hallowstume pumpkin costume at level 37.
Costume Pokemon
Type: Fairy/ Grass
Ability: Unaware/ Gluttony/ HA: Shadow Tag
Height: 1.60m
Weight: 187 kg
Signature move: Gourd Bomb*
Dex entry: It evolves when it identifies completely with the pumpkin costume. Pumpstume have the ability to greatly extend the vines on the head by eating nutrients.
*Gourd Bomb: Type: Grass; Category: Special; PP: 15; Power: 85; Accuracy: 95%. 30% chances to confuse the target.

SKELESTUME
Evolves from Hallowstume skeleton costume at level 37.
Costume Pokemon
Type: Fairy/ Ground 
Ability: Unaware/ No Guard/ HA: Shadow Tag
Height: 1.40m
Weight: 56 kg
Signature move: Dead land*
Dex entry: It evolves when it identifies completely with the skeleton costume. Skelestume have the ability to remain underground for many years before rising to the surface.
*Dead Land: Type: Ground; Category: Physical; PP: 15; Power: 85; Accuracy: 95%. 30% chances to confuse the target.