unicorn mtg cards Prized Print put a +1/+1 counter on that creature. Kauê Daiprai - Steadfast Unicorn

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

For the former, the sheer number of creatures in the deck helps

0 is standard, going negative causes the spring to ease up, going possitive causes the spring to tension more

Combined with Mind's Desire's ability to reduce the top card of a library to nothing, players have found ways to play a tremendous amount of cards in a single turn

We get so many cool tribes to play with in MTG, and building a perfect tribal deck using all of the right cards is a huge amount of fun