As a Commander finisher, it doubles down in decks led by Xenagos, God of Revels or Aurelia, the Warleader
Same with a charge counter: If you move a charge counter from The Seriema to a Forest, then the counter just sits there charging nothing
15 cards per pack, 30 packs per box
If you somehow can't discard a card (probably because you had no cards in hand and another effect prevented you from drawing cards), you won't put any counters on Cait no matter whether or not the defending player discarded a card or what that card's mana value is
Cards that care about mana value like Caustic Bronco, Sorin, Grim Nemesis, or Twilight Prophet are good incentives to have expensive cards around
Hand disruption is always good, and the potential to set your opponent down to just one card in hand with a single Supporter is obscenely strong