You can't have more than 1 Radiant Pokémon in your deck.
If this Pokémon is in the Active Spot and is Knocked Out by damage from an attack from your opponent's Pokémon, search your deck for up to 3 cards and put them into your hand. Then, shuffle your deck.
Flip 2 coins. If both of them are heads, your opponent's Active Pokémon is Knocked Out.