The northern corridor was the only clean route left between the Grand Hall and the lower district, which meant it was also, within about ninety seconds of Isaac reaching it, the most contested twenty feet of hallway on the entire island.
He'd frozen the floor first. Instinct more than plan, a wide sheet of ice spreading out from where he stood, rough enough that fleeing students could still get traction if they were careful, smooth enough that anyone trying to charge through at speed went down hard. It bought him a few seconds. He used them to freeze the ceiling supports next, thick columns of ice locking three structural beams in place that had already started to crack from something happening two floors up.
Students streamed past him in both directions, some heading for the exits, a few of the older ones peeling off to actually fight, robes and uniforms torn, faces set in the specific grim calm of people who'd trained for exactly this kind of day and never expected to need it.
