When a Pokémon with the Mummy Ability is hit by an attack that requires physical contact, the attacker's Ability becomes Mummy, disabling the attacker's Ability in the process. The attacker's Ability remains disabled until it is defeated or substituted.
Mummy doesn't have an effect in the Overworld.
Pokémon With Mummy
Related ThreadsThe Mummy (2017) - last post by @ Jun 7, 2017
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