Dreamscape Travels was a side quest that William had undertaken before.
One day, a sudden plague swept through a remote town, leaving the residents unable to sleep and only accumulating fatigue until they fell into intense hallucinations.
A strange foreigner arrived in town and claimed to be able to cure the plague.
After earning the trust of the townspeople, the foreigner concocted a green potion using alchemy materials and a hallucinatory tree sap. The townspeople drank it and were able to fall asleep and dream, but their dreams were anything but peaceful.
The Moon Realm was known for its nightmares, and the souls of those who drank the potion were controlled by the Lord of Nightmare, Zamara, and fell into an endless nightmare.
William remembered drinking the potion and being transported to the Nightmare Swamp, where he successfully saved the townsfolk in that strange dream.