Furtive Courier

The evasion clause is what marks this as an artifact-sacrifice payoff first and a Merfolk second: unblockable turns on only if you've sacrificed an artifact that turn, which means the body is slippery only inside a deck already spinning treasures, clues, or fragile trinkets through a sacrifice outlet. That gating is the interesting part. A 3/2 that draws-then-discards on attack is a modest looter on its own; wire it into an engine that generates disposable artifacts as a byproduct, and the same combat step becomes a guaranteed connection plus a card-filter trigger. The loot underwrites the aggression: attacking into an open board with a hand you want to smooth is where the ability earns its keep, digging toward the next payoff while the artifact fodder keeps the creature honest about slipping through. The design leans on the reader recognizing that blue rarely gets reliable evasion without strings; here the cost is measured in permanents you were already planning to feed to something else. Absent a deck built to sacrifice artifacts routinely, the unblockable clause simply never fires, and what remains is a fair-rate creature with a loot attached. It is a rider that asks the rest of the deck to have already answered the question of what you are sacrificing and why.