Teferi's Wavecaster

A tutor stapled to a body, and the target it fetches tells you everything about the intent: this Merfolk exists to find Teferi, Timeless Voyager and nothing else. The load-bearing choice is that it searches both library and graveyard, which turns a discarded or destroyed planeswalker back into a live threat rather than dead cardboard. It is one half of a package printed alongside its specific planeswalker, so building around either makes the other reliably castable. Flash is what elevates it past a vanilla tutor-on-a-stick: holding up five mana on an empty-looking turn lets you fetch the planeswalker at instant speed, drop the 3/3 as a surprise blocker, and set up a threat you never telegraphed. That instant-speed window also lets the body bait removal or slip in when the coast is clear, so the card's real job is controlling when the planeswalker arrives rather than trading in combat. Left to itself the Wavecaster is a fine flash blocker that finds a card you may not always want; alongside its partner it becomes a consistency engine, the piece that makes a singleton planeswalker behave like a four-of.