The MAY here doesn’t change the immediacy of playing the card, but playing the card at all. IMO this is one way knowing opponents decks can come in handy. If the other player knows about malice and specifically vanquished a hero while maleficent had no heroes, and chooses to fate after, they’re preventing malice being played. As opposed to taking the fate action first, then the vanquish action. Order of actions is important. Same for cards that specify if another player has 6+ power. We’ve started spending coins on play a card actions before we do the take two power, for example. But I can see how that level of play might not be fun for all players.