Iona, Shield of Emeria
Most prison effects tax or punish; this one simply deletes. Choosing a color and locking your opponents out of casting it is the most absolute color hosing ever stapled to a creature, a binary switch with no workaround other than removing the body itself. Against a mono-colored deck it is game over on resolution: there is no payment, no exception, no instant-speed escape valve, only a 7/7 flier closing out a turn count with the opponent's hand frozen solid. The nine-mana cost is what holds the card in check. At that price it is not meant to be hardcast on curve; it is a reanimation and cheat-into-play target, the payoff that makes a turn-three Iona feel less like a haymaker and more like a concession demand. That asymmetry, trivially cheap to deploy through Reanimate or Sneak Attack and brutally lethal to a focused decklist, is exactly why it became a canonical reanimation finisher. What makes it more than a fat angel is the sheer refusal to negotiate. Cards before and since have asked opponents to pay more or jump through hoops; Iona just builds the wall and dares you to find a door.
