Reveal cards from the top of your library until you reveal a creature card. Put that card into your hand and the rest on the bottom of your library in a random order. When you reveal a creature card this way, put X +1/+1 counters on target creature you control, where X is the mana value of that card.
If the revealed card has {X} in its mana cost, X is 0 for the purpose of determining its mana value.
2025-06-06 • wotc
You don't choose a target for Yuna's Whistle at the time you cast it. Rather, a second "reflexive" ability triggers when you reveal a creature card this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.