Harness by Force

Threaten effects had always been single-target affairs: steal one creature, swing, sacrifice it before it goes home. Strive rewrites the math by attaching a scaling tax to the count, so the question stops being "which creature do I take" and becomes "how much red mana am I willing to convert into an army for one turn." Each additional target costs more, which means a wide opposing board becomes a deeper well to draw from rather than a wall to break through: the more bodies they have committed, the more this can flip back across the table, provided the mana is there to cover the tax. The haste-and-untap clause is what makes the multi-steal coherent rather than cosmetic: tapped-out defenders and summoning-sick walls all come online as attackers at once, and the temporary-control window lines up perfectly with a sacrifice outlet, since the creatures revert at end of turn anyway and feeding them to something first denies the opponent the return. That is the structural logic worth noting: each new target raises the price, but the payoff is a one-turn alpha strike assembled entirely from your opponent's board. As a sorcery it asks you to commit on your own main phase, with no instant-speed ambush, which keeps the effect honest against a defender who can see it coming. Where older single-target steal spells were a tempo trade, this one is a finisher: a red answer to a stalled board that turns the opposing army into the closing swing.