Ability₁₀₉-Imposter

As soon as the user comes into battle, it transforms into its opponent.
⚠️The target's appearance (including form), types, Ability, stats, and moves are copied; the user retains its HP and level.
⚠️Imposter will not activate if the opponent is transformed, is disguised with Illusion, is behind a substitute, or is a Starmobile.
⚠️Imposter only activates when the Pokémon with the Ability is sent out; if it fails to transform into an opponent, it will not activate unless the Pokémon with Imposter is withdrawn and sent out again.
⚠️Imposter will also not activate when obtained during battle.
⚠️If a Pokémon with Imposter Terastallizes into the Stellar type, Imposter will no longer activate.
⚠️In Double Battles, Triple Battles, and Battle Royals, Imposter will target the opponent in the position directly opposite it.
⚠️If there is no opponent directly opposite it, it will not transform.
⚠️In Horde Encounters, Imposter will copy the opponent in the right-most position.
⚠️If the opponent of a Tera Raid Battle has Imposter, it will transform into the host's Pokémon.
⚠️Role Play fails if the target has the Ability Imposter.
⚠️Entrainment fails if the user has the Ability Imposter.
⚠️Imposter cannot be copied by Trace, Power of Alchemy, or Receiver.
~Bulbapedia