Lavinia of the Tenth

The mana-value-four-or-less clause is the whole architecture here, and it tells you exactly what this card was built to police. Detaining each cheap nonland permanent on entry isn't a sweeper or a tempo swing against a midrange board: it's a tax aimed squarely at the low end of the curve, the aggressive starts and the small interactive pieces that win on the second and third turns. Everything heavier than four mana walks through untouched, which means a five-mana body that taxes cheap things is, by design, a creature that arrives once the early game is already a question and answers it on the spot. Protection from red sharpens the point in the same direction: the color most associated with going under a control deck cannot block her, burn her below her range, or punch through her 4/4. She is, structurally, a guard posted at the front of the curve. Detain is the right verb for that job, too. It does not exile or destroy; the affected permanents stay on the battlefield the entire time, simply unable to attack, block, or fire their activated abilities until your next turn. That single turn cycle is the whole bargain: the controlling deck buys exactly the window it needs to stabilize, and when the lock lifts the tempo math has already flipped. That temporary, conditional quality is what separates her from a board wipe and what locates her firmly among the white-blue answers that prefer to slow a game down rather than reset it.