Choose 1 of your opponent's Evolved Pokémon (excluding Pokémon LV.X). Remove the highest Stage Evolution card from that Pokémon and put that card back into your opponent's hand.
When you attach a Water Energy card from your hand to Helix Fossil (excluding effects of attacks or Poké-Powers), search your deck for a card that evolves from Helix Fossil and put it onto Helix Fossil (this counts as evolving Helix Fossil). Shuffle your deck afterward.