Storm King's Thunder
Brash is a tiefling wizard that the party first heard about in 1372 DR in Waterdeep. Although they never tracked him down, they felt his influence.
After a night of drinking with their friend and patron Nuvruil, the party awoke naked and hung over in a cave off the Sword Coast. It turns out, Brash, under the guise of Nuvruil had tricked them the whole time, having them collect ingredients or artifacts (frankly no one insisted on getting any answers), then drugging them and throwing them through what turned out to be a portal carrying them into the future.
Brash was quite gloaty in the message he magically recorded for them, and now they seek revenge upon him. If he still lives. And if they can find him. And if he is still alive and hasn't spent the last hundred or so years getting more powerful. Time will tell.