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.