Go to the Oneiromancer and ask her for help. She will tell you to make a vision potion and gives you a Dream vial. To make the potion, you need to fill the Dream vial (empty) with water to create a Dream vial (water) - The easiest way to fill the vial after obtaining it is in the house southwest of the bank on lunar isle. Next, add a Goutweed (either grown through farming or stolen at troll stronghold) to create a Dream vial (herb). Finally add Ground Cosmic rune (use a hammer on an Cosmic rune, then crush the shards into dust with pestle and mortar) to make the Potion of Shared Vision. Return to Ali the Hag.