Sanctum Prelate

Where most white hatebears tax a whole category or shut off a color, this one deletes a single point on the mana curve. Naming a number rather than a card type means the lock follows your read of the room: call one against a deck leaning on Lightning Bolt and one-mana cantrips, call two against the format's removal staples, call zero to shut off the spells that cost nothing at all. The cost of that flexibility is its opposite. The number locks the moment the creature enters, and noncreature spells at any other value sail through untouched, so a misread leaves the opponent a whole curve to operate on. It is also a 2/2 with no protection, which puts the entire prison one removal spell away from collapsing (the same removal it can shut off only if you happen to have named its cost, which the opponent will not oblige if you guessed elsewhere). The lineage is the value-locking wing of white disruption: Thalia, Guardian of Thraben taxes broadly, Gaddock Teeg bans a range outright, and this trades their always-on rules for a scalpel that demands you already know what the table is trying to do. It rewards the player who can identify the one spell that breaks the game open and excise it, and does nothing at all to the deck it guessed wrong about.