Shadowy Concealment

If 1 of your Darkness Pokémon is Knocked Out by damage from an attack from your opponent's Pokémon ex, that player takes 1 fewer Prize card. The effect of Shadowy Concealment doesn't stack.

Rules

Pokémon ex rule: When your Pokémon ex is Knocked Out, your opponent takes 2 Prize cards.

Mega Evolution ex Rule: When your Mega Evolution Pokémon ex is Knocked Out, your opponent takes 3 Prize cards.