Hawk Diesel
Adventurer
Not sure if anyone cares, but I have written out the ending of CoS, and have gone a little more simple than what was above.
Basically, I'm going with Barovia needs a King or else the Dark Powers are freed. Strahd can leave if Tatyana's soul goes with him, leaving Barovia without a King, freeing them and allowing Strahd to go out into the world.
When Strahd dies, the Dark Powers will appear and inform the players that either one of them takes his place, or they are loosed on the worlds. In order for one of them to take his place, they must kill one of the others, which makes them turn into either a Lich or a Vampire, or Death Knight, they're choice, and they become the new Lord of Ravenloft. At that point, the other two are allowed to leave, so long as the new Lord of Ravenloft allows them to.
I'm doing it this way because Curse of Strahd is a horror book, and it should have hard consequences. Becoming the Lord of Ravenloft shouldn't be just some willy nilly "Oh, I perform this ritual" or "Oh, I kill this random NPC." I want it to be hard. If my brothers want the throne, they're going to have to pay for it.
What I expect to happen is for my two brothers to look at each other and say "Duel to the death?" And the other to answer, "After you, old chap." And this would be after fighting Strahd, so it'll be interesting to see what happens.
But if they DON'T, and it's likely they won't since I will make it clear that being the Lord of Ravenloft is just as much a curse as anything, then the Dark Powers are freed, and I'm considering running Tomb of Annihilation next, with the Dark Powers being responsible for the Death Curse, and they have to find a way to stop it. I'm really hoping they take this option, but knowing my brothers, probably not.
I guess my only question would be, why don't the Dark Powers want to be freed? Wouldn't they be motivated to allow Strahd to die and no one take his place? This could work if revealed by a scholar or text prior to the showdown, but I don't see the Dark Powers delivering this message/choice.