Jace reached the Seedcore with the weapon, but infection had turned his remaining time into a countdown. The original plan depended on destroying Realmbreaker before it connected to other planes. By the moment he prepared the Sylex, the branches had already begun touching the Multiverse.
Activating the device could still kill the tree and New Phyrexia. It could also carry the detonation through those connections, making the rescuers responsible for devastation on the worlds they meant to protect. The weapon offered certainty only by ignoring where its consequences would travel.
Jace continued because he could no longer trust that another opportunity existed—or because the infection was already reshaping what he considered acceptable. Around him, allies argued inside seconds that carried the weight of planes. The mission had reached its target and lost the moral clarity that made reaching it meaningful.