Mega Spiritomb: Breaks out of its OddKeystone (look at its lore) so it can roam freely
Dark/Ghost
dont know, in PokemonInsurgence Spiritomb has Noctem that casts a weather ability that increases Dark/Ghost moves by 50% and decreases fairy moves by 50%(not saying thats what you should put) but something that makes it not weak to Fairies because Spiritomb having a weakness doesnt feel right
HP: 50
Attack: 108
Defense: 108
Sp. Attack: 108
Sp. Defense: 108
Speed: 108
Its a 105 stat increase but not all megas have a 100 stat increase. 108 Stats because of lore