Invulnerability

Buyback was Tempest's experiment in making instants permanent, and this card is the data point that shows where the mechanic's appeal actually comes from. Strip away the buyback and you have a Fog for your face: choose a source, prevent the next chunk of damage it would deal you this turn. That's a reactive, narrow play even at two mana, the kind of thing that wins a race by a turn or absorbs a single attacker. Buyback is the lever meant to elevate it, letting you recast the spell instead of spending it: five mana total ( plus the ) to keep the card after it resolves. But the prevention is capped at one source and one instance per casting, so the loop costs you that mana every turn to blank a single creature or burn spell while everything else keeps swinging. The friction that justifies buyback elsewhere (Whispers of the Muse, Capsize) is real value generation paid out over time; here the recurring payload is too small to earn the recurring tax. What the card documents is the design lesson that buyback's value scales with how much the underlying spell does, not with how cheaply you can rebuy it. A reusable prevention shield reads powerful until you notice it only ever shields against one thing at a time.