Dungeons and... that's it, probably.

Ask the Plague Doctor in the Abandoned Tower how to make Dream Dust.

To finish it: choose Dream Dust. when talking to Albert.

Completed

Now I can brew potions in the Abandoned Tower.

Comes after

• Dungeons and... that's it, probably. — Open the hatch and let the Plague Doctor into the tower.

Leads to

• Sweet Dreams — Bring the Dream Dust to the Plague Doctor in the Abandoned Tower.