Levitate

Levitate is an ability in Polished Crystal that grants the Pokémon immunity to all Ground-type moves and the effects of Spikes, Toxic Spikes, and Arena Trap. This means that Pokémon with Levitate cannot be affected by moves like Earthquake, Dig, or any other Ground-type attacks.

Air Balloon does something similar but only until the user is hit. Levitate is a permanent ability that does not require an item to function. In Polished Crystal, Levitate can be found on several Pokémon that generally hover - including Gastly, Haunter, and Gengar.