Wake the Dead

The casting restriction is the whole design: this resolves only during combat on an opponent's turn, which turns a temporary reanimation spell into a combat trick that returns an entire army. You wait until an opponent has committed attackers, then bring X creatures back to gang-block, eat the swing, and harvest whatever enters-the-battlefield and leaves-the-battlefield value those creatures carry on the way in and out. The returned bodies do not stick: they get sacrificed once combat wraps and the turn winds down, so the cards you fetch are never lasting investments. They are ambush blockers and trigger fodder, nothing more. That timing window is the axis the whole card turns on, and it is what makes the spell look clunky in isolation yet play like a blowout. The X cost lets a single instant rebuild a board mid-attack, while the sacrifice clause denies you any permanent gain from it, keeping the exchange from being pure profit. Built for graveyard-dense black decks where the returned creatures are engines rather than blanks: a death-trigger drainer, an enters-the-battlefield removal creature, a sacrifice payoff that wants bodies at the door regardless of how briefly they stay. The trap is expensive to spring, but it springs only after the attacker has already passed the point of no return, having committed to swinging into an untapped board with two black sources and X more mana held behind them.