Just once per attack, no matter how many get their swing on
Building powerful decks in Pokemon TCG Pocket is a combination of clever strategy and good luck
Effect Veiler, Infinite Impermanence, or even Forbidden Droplet (assuming the opponent did not send a Spell to their Graveyard) are examples
Specifically, the Pokmon Company said that " Removing this card from the environment will affect how many decks are constructed, which will hopefully make the Expanded format feel fresh and different
Let's start with Primitive Justice and Silverback Elder
In order to compete in the World Championship in this structure you must have placed top four in MPL, placed top four in the Challengers/Rivals League, won one of the seven tabletop or arena Mythic Championships, or won of the previous year's World Championship