Variation

the item that acts as the catalyst to move the Subjective Story Throughline forward

The Subjective Story Throughline Catalyst is what creates breakthroughs and seems to accelerate the Subjective Story Throughline. In both the Objective Story and Subjective Story Throughline there occur dramatic "log-jams" when things seem to be approaching a halt. This is when the Catalyst is necessary, for its introduction will either solve the puzzle that's holding things up or else make the puzzle seem suddenly unimportant so the story can continue.