Mysterious Fossil.

Play Mysterious Fossil as if it were a Basic Pokémon. While in play, Mysterious Fossil counts as a Colorless Pokémon (instead of a Trainer card). Mysterious Fossil has no attacks of its own, can't retreat, and can't be affected by any Special Conditions. If Mysterious Fossil is Knocked Out, it doesn't count as a Knocked Out Pokémon. (Discard it anyway.) At any time during your turn before your attack, you may discard Mysterious Fossil from play.