Chromeshell Crab

Most control-magic effects let you keep what you take; this one trades. The face-up trigger exchanges control of a creature you control for a creature your opponent controls, which means the chump token, the mana dork, the morph that turned out to be nothing all become exit ramps for stealing the best body on the other side of the table. That asymmetry is the design idea: you are not just grabbing their fattie, you are handing them your worst creature in the process, and the worse your fodder, the better the deal. The morph shell hides both the threat and the trade: paying three to drop it as a face-down 2/2 means the opponent commits to the board without knowing the unmorph is going to walk off with their best creature, and flipping it up at instant speed lets you ambush a freshly resolved threat. It even turns removal into a windfall: when an opponent points a kill spell at one of your creatures, you can respond by trading that doomed creature away for theirs, letting the spell finish off what is now their problem while you keep the prize. The crab body underneath is incidental, a vessel for the trigger and a payoff for the morph. What sets it apart from borrow-and-return effects is permanence: the swap does not revert, surviving the end of turn and the loss of the source. An early-era oddity that reads like a Johnny puzzle and plays like one, rewarding boards where your worst creature is genuinely worthless.