Café de Nuit

Yes it would have been cataclysmic but only in Ravenloft. Unlike the GC or Vecna's escape, the Shroud wouldn't have spread to Toril or Krynn.

I also agree the ToUP should be limited to Ravenloft.

To really get at it, you have to decide, what is worse than the Darklords or Dark Powers? That is probably at the core of the ToUD, as it should scare both of those groups.

worse than Darklords or DP's....the Lady of Pain "mazes" the DP's

Aesthetically, I think the story with Ravenloft is that it's self contained. Also, the Dark Powers limit their manipulations, for the most part, to inside the demiplane.

For a Time of Unparalleled Darkness, I think it would be in good keeping with reversing that neat introversion. Also, you have the problem that the Grand Conjunction has already happened, and theoretically exposed every single prime world to a brief period of Ravenloft rules and Dark Powers checks (not to mention wandering werewolves and ermordenung). In my opinion, TSR lost a good chance to drive home the enormity of this situation - it's never really referenced in any other campaign setting. If they had worked that into the updates for Greyhawk, Forgotten Realms, and Dark Sun - even if it was just a footnote of a misty period of time where abominations walked the earth - that would have been very cool.

If you're going to limit the ToUD to just Ravenloft, then it's a bit of a damp squib in my opinion. I'm hard pressed to come up with anything better than the GC but it should be on at least the same scale, I feel.

Hmmm...an interesting thought. I imagine the biggest protest RL GMs and players would display is: Well, fine, so the Time of Unparalleled Darkness affects other worlds in the Multiverse...but what has that got to do with MY campaign...?

I do like the idea, though, of--even if for a brief time--the demiplane's rules reaching out and affecting creation at large...

An idea:

In the Time of Unparallelled Darkness, Ravenloft begins invading other planes and settings, taking them over and turning them into domains. Doing so begins to expand the power of the DPs to all new levels...

I would say that as Ravenloft is a prison, a time of unparalelled darkness would be - breaking of chains and walls.

Ravenloft would be coterminous with other planes, maybe in place of the Ethereal plane. Domains would no longer imprison darklords, and they would be free to wander the whole Ravenloft and multiverse. They would retain their domain powers - but they would apply to any land they would conquer. They would be also freed from those curses which stop them from conquering and destroying.

Vlad Drakov would at last be able to march out of Falkovnia, bringing fire and sword to Borca etc. Azalin would learn new, deadly spells and try to reconquer his homeland, impressing his subjects into his (undead?) army of conquest and killing them to fuel his necromantic spells. The four riders would ride out of Necropolis.

And, at last, the immense form of Gwydion would climb out of the Rift and standing atop Mount Keening, reach out a long hand to shatter the Sun.

Any world to which darklords went would slowly change into Ravenloft and join to it- but not as a new domain, since there would be no more domains.