Torrential Gearhulk

The flash on a 5/6 body is doing two jobs at once: it makes the construct a credible blocker that ambushes attackers, and it turns the enter trigger into an instant-speed window. That second function is the whole design. Holding up six mana, you represent both a hard cast on your opponent's end step and a recast of any instant already in the graveyard, so a sweeper, a counterspell, or a removal spell gets fired a second time on a body that often survives the turn. Earlier graveyard-recursion finishers leaned on sorceries or general spell recall; restricting the rebuy to instants is what keeps this from spiraling, since the trigger respects the same timing the card itself uses. The exile clause is the tax that pays for the value: whatever you flash back is gone for good rather than feeding a loop, so each Gearhulk converts exactly one instant in the yard into one free cast plus a hard-to-kill blocker. That math is clean enough that the card behaves less like a creature and more like a removal spell or counterspell with a 5/6 stapled on, deployed at the moment of maximum information. The body matters too; six toughness shrugs off most of the burn that would punish a blue control deck for tapping out, and five power closes games faster than the usual blue endgame.