add a villain or heighten the villain’s opposition provide discovery or knowledge that illuminates the past, or (better) will be needed to solve the overall problem show learning or practicing a skill that will be needed to finish the quest add a tool or weapon to the protagonist’s arsenal (doesn’t have to be literal: “self-confidence around my crush” is also a tool) test the preparedness of the protagonist or team cause a setback to the protagonist or team, or damage the villain handicap the hero by causing a significant and lasting impairment
