Higher-level play

Past level 6, PCs become increasingly competent and harder to challenge. They have better stats, more ways of generating advantage, and lots of tools for overcoming challenges and mitigating dangers. They can start to feel invincible.

To continue challenging higher-level PCs:

Up the stakes. Use foes with messy attacks and moves that inflict lasting harm. Don't just threaten the harvest, threaten Stonetop itself. Don't just threaten the village, threaten the region as a whole.

Make 6- results hurt. High-level PCs roll low less often, so go hard when they do. Capture them. Reveal a betrayal. Destroy a prized possession. Sever a limb. Kill a loved one. Be irrevocable.

Be aggressive. Keep making soft GM moves, any chance you get. Make moves that affect multiple PCs. Make moves that force them to react before they can do what they want.

Hit them where they're weak. Look for ways to make them roll their lower stats. Threaten vulnerable NPCs and resources.

Make them choose where to focus their efforts, and make those choices matter. Present threats on multiple fronts. Whatever they don't deal with should escalate, go poorly, or have repercussions.

But also—and this is important—let them enjoy their wins. Give them chances to steamroll challenges that previously would have given them pause. Celebrate their competence and their accomplishments. Then, when you do challenge them, it'll feel all the more dire.