Dark Omastar

Nothing can escape once wrapped in its tentacles, which it uses for self-defense as well as to catch food.

Prehistoric Water: If your opponent has any evolved Pokémon in play, choose 1 of them and flip a coin. If heads, your opponent takes the highest Stage Evolution card on that Pokémon and shuffles it into his or her deck.

Dark Tentacle (30): During your opponent's next turn, the Defending Pokémon can't evolve except from effects of attacks or Pokémon Powers. (Benching that Pokémon ends this effect.)