Horned Loch-Whale // Lagoon Breach

The instructive half here is the instant, and its cleverness is in what it refuses to do: Lagoon Breach doesn't kill an attacker, it un-declares one. Cast during combat, it pulls a single attacking creature you don't control out of the fight and buries it on its owner's choice of top or bottom of their library, erasing a hasty threat outright or costing a slower one a full draw step of tempo. Because nothing dies, it slides past regeneration, indestructibility, death triggers, and the graveyard-value engines that would happily accept a corpse. The constraint is that it only touches attackers: reactive by construction, a combat-phase intervention rather than open-ended removal. The creature side reads like a flash blocker but is engineered not to be one. "Enters tapped unless it's your turn" punishes the obvious line, since flashing it in mid-combat to block leaves it tapped and useless. The real payoff of flash is holding mana open through the opponent's turn for instants, then landing the whale on their end step: it still enters tapped, but untaps immediately as your turn begins, ready to swing. So the two halves divide labor rather than rhyme. One unwinds an attack at instant speed; the other converts a turn spent holding up mana into a 6/6 whose Ward taxes the removal that would answer it.