Cool.
The gist of it is this: In my campaign, the elf rogue PC suffered a head injury that gives him the
confusion-based madness effect from the DMG. He's been seeking a cure, and while a human paladin did offer to help him, he decided he didn't want to be beholden to any human gods. So he's been keeping an eye out for an elf priest who might be able to help him instead.
Since he's currently in an area where it is unlikely that there would be an elf cleric of high enough level to cast
greater restoration, what I was thinking was that when he goes to the local shrine to the Seldarine, the priestess could suggest that the gods themselves might be willing to help, if he opens himself up to their influence. She'd then get him to drink from a sacred pool at the shrine or something, whereupon he'd fall into a trance and experience a waking vision, which would consist of iserith's
Barrow of the Evensong adventure, except that instead of having the portal lead to Arborea, it is the "way out" of the vision. If he successfully completes the quest, he'll be cured of his affliction.
His companions will be there with him - but whether they're really there, or they're just figments of his imagination, is open to interpretation. But at least one bit of treasure will come back with him into the "real world". So whether it's just a dream or was some kind of alternate reality ... who knows? The gods work in mysterious ways, right?