Claydol

An ancient clay figurine that came to life as a Pokémon from exposure to a mysterious ray of light.

Antique Magic: Put 3 damage counters on any Pokémon (both yours and your opponent's) in any way you like.

Synchro Attack (30): If the Defending Pokémon has the same remaining HP as Claydol, this attack's base damage is 90 instead of 30.