Day 19 - Retractor - Helpmate

The energy pulsing through the station begins to fade, but the air remains heavy with tension. David studies the readings on the console. “These gravitational distortions aren’t just random. Grinchuk is channeling the TSC’s power into something bigger.”

Santa steps closer. “What exactly is he building?”

David hesitates, pulling up a schematic on the console. The glowing lines form the outline of a sleigh, surrounded by swirling energy fields. “It’s… a sleigh,” David mutters. “But this isn’t like yours, Santa. It’s designed to exploit time dilation directly.”

Magnus leans in, “Explain.”

David takes a deep breath and points to the outline on the console. “Grinchuk’s Chrono-Sleigh is trying to replicate your sleigh’s ability to bend spacetime, but with one difference. Instead of slowing time for himself, he’s aiming to create a closed time loop - one where he controls every moment of Christmas, rewriting history to make himself the central figure.”

Wesley stares at the schematic. “So he’s not just trying to sabotage us. He’s trying to… erase us?”

David nods grimly. “If he succeeds, the TSC will lose its stabilization anchor, and the black hole’s gravitational pull will drag the entire timeline into his loop.”

Santa’s voice is calm but firm. “Then we stop him. Where is he?”

David glances at a new signal appearing on the console. “His Chrono-Sleigh is in the cavern directly beneath this station. The gravitational field down there is dangerously close to the black hole’s ergosphere. If he activates it, the timeline could fracture permanently.”

Magnus gestures to a hatch at the far side of the room. “We have to act quick.”

Before Santa can respond, the console flares brightly, showing a distorted timeline diagram—moves made, but reversing themselves in a recursive pattern. David’s eyes widen. “He’s already begun testing his loop. He’s reversing moments in time to see if the changes hold. If we want to fix this, we’ll need to undo the sequence and realign it.”

In the current position, White has just completed a move. First, undo the last move made by White, followed by undoing the last move made by Black. Then, resume the game by making a move for Black, and finally, a move for White. White’s last move should deliver checkmate. This is a help-retractor, so both players cooperate.

You do not need to provide the two retracted half-moves in the solution, only the two moves being played forward after the retraction. First a Black move, then a White move, delivering checkmate