Demonic Dread

The cheapest possible delivery vehicle for cascade, and the trigger is the entire reason to play it. A falter spell that costs two-or-less would be filler; stapling cascade to it for one more mana turns the card into a free spell plus a bit of evasion every time you cast it. Because cascade reads down to anything cheaper than this spell's three mana value, it can hit two-drops, one-drops, or even a zero-cost spell waiting in the deck, most often a setup piece you would happily land for free while poking a creature off blocking duty. The "can't block" clause is the constraint that prices the whole thing: this is a target-requiring spell, so it cannot be cast when no creature is in play at all, which means the free cascade only fires when there's a creature on the board to target. The target need not be an opponent's, though: you can point it at your own attacker to satisfy the requirement, which keeps the spell castable even when the opposing board is empty. That flexibility is what separates it from a strict removal-adjacent effect; the falter is almost incidental to the cascade payload. Cascade remains one of the more dangerous keywords Wizards prints precisely because deck construction is the only dial on what it finds, and this sits at the floor of that cost curve: a tool for triggering the keyword, not a payoff in its own right.