Starting with the next opponent in turn order (or, if you cast Flare of Malice on an opponent's turn, starting with the opponent whose turn it is) and proceeding in turn order, each opponent chooses a creature or planeswalker with the greatest mana value among creatures and planeswalkers they control to sacrifice
To do that, you compile a deck of at least 60 cards (maximum copy of any one card is 4) utilizing two of the six Ink colors
So if you like the idea of a Tokens deck like Rhys the Redeemed but with a Cat Tribal theme, then swapping Arahbo, Roar of the World for Mirri, Weatherlight Duelist is a simple yet highly effective way to start on that route
It's a useful card that sees plenty of action in Commander, but the Japanese Silver Scroll variant is stunning and really makes it one of the most vibrant cards in the set
My guess is that if they did vote it down to 10, we might see a rash of infect decks and a drop in the number of players who think the league is "fun"