Shields Down (ability)
Shields Down causes the Pokémon to changes its appearance and stats depending on its remaining HP.
When the Pokémon's HP is over 50%, it has higher defenses and is immune to status conditions. When its HP falls below 50%, the outer shell breaks and the Pokémon has higher attack.
Ultra Sun/Ultra Moon
|When its HP becomes half or less, the Pokémon’s shell breaks and it becomes aggressive.|