While Snow Mercy only gives those creatures counters, you can use Snow Mercy to tab down those creatures, and the fun part here comes with how you activated that ability because you have to tap, then untap, then tap, then untap, then tap Snow Mercy
Since we usually have a flicker effect at our disposal, we can typically bypass the need to hardcast these creatures, however, there will be rare occurences where we may need to use Prophetic Prism to fix our mana and simply cast our oddly colored threats
Thats clues, treasures, food she turns the lot into mana
Whether youre casting Damnation for the second time because your opponent was packing a Heroic Intervention the first time or youre attempting to power out a game-winning Ad Nauseam after surveilling it to your graveyard off of Dragons Rage Channeler earlier in the game, Maestros Ascendancy is sure to give you a lot of value for just three mana
This creates a loop of legendary threats, making them feel nearly immortal
It might not fit in the average cast-from-exile deck, but the ones that support it will go off like fireworks