Ghost / Psychic
Gives full immunity to all Ground-type moves.
Powers up Fire-type moves in a pinch.
A Trainer with a Delphox once walked into a Haunted House, looking for Ghost- Type Pokémon. The Trainer got scared by the cries of a wild Mismagius, leaving the Delphox there. The Delphox, feeling abondoned, started living in the Haunted House. It eventually adapted to its environment, and became part Ghost- Type.