Cloud Cover

The defensive answer to spot removal that turns every kill spell into a tempo wash: point a Murder at one of your creatures and it goes home instead of dying, and the opponent has spent a card to make you replay a permanent. What sets this apart from a counterspell or a protection enchantment is that it sits passively on the battlefield, taxing the opponent's entire removal suite while it survives, and it reaches anything you control: a creature, a key artifact, even an Aura or another enchantment. The wrinkle worth understanding is that the trigger fires on targeting, so it answers single-target burn and tap-down effects, but it does nothing against board wipes, against sacrifice clauses that never name a permanent, or against edicts (which target the player and force the choice from your side, never putting your permanent in the crosshairs). The return is also a may, which matters more than it looks: you can decline to save a permanent you would rather see leave (a creature with an unwanted Aura, a token that would evaporate in hand anyway), and you can choose to rescue and rebuy your own enters-the-battlefield triggers when the opponent obliges by targeting them. It is a finicky, conditional piece, the kind of soft lock that rewards a board built around permanents the opponent must answer, and it has stayed a fringe blink-and-protection curio rather than a staple precisely because the protection is narrow and the cost is high for what amounts to a one-permanent-at-a-time shield.