Because the ability to buy individual cards is so helpful, you should only ever spend these when building a specific deck
I can also do everything Im trying to do without splashing green, using Devious Cover-Up, which I absolutely love, but its a little clunky and doesnt let me go huge with The Mending of Dominaria, though that might not be necessary
Being combined with tempo cards of the day like Winter Orb, they'd make the cut in powerful decks called "Frozen Fish" and then after the first typal set ever printed, Fallen Empires pushed the Merfolk creature type as a supported group even more
It doesn't work with blink or reanimation though
Cascade, cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less You may cast it without paying its mana cost Put the exiled cards on the bottom of your library in a random order Then do it again.)