In all the cases I can remember in which somebody got taken by the mists to become a Dark Lord, it happened to an unwilling subject (which makes sense, given the torment they suffer there).
Let's imagine the situation where somebody knowledgeable about Ravenloft lore would try to get the Dark Powers to kidnap him, along with his domain, into Ravenloft on purpose. To make the situation even worse, his ultimate motives might be honorable – he knows that if his castle stays in the Prime Material plane for another month, the entire plane will get destroyed (or at least very seriously damaged, a mass extinction kind of event). Let's assume no frame challenges on this point – destroying the castle itself is not an option (it won't help and moving to other plane than Ravenloft is also not possible).
From a very good description about Dark powers, we can read:
The Dark Powers seek those who transgress. Those who become Darklords are guilty of deliberate, passionate evil, often done in full knowledge that the deed was wrong. Whether the nascent Darklord is a deluded oathbreaker like the Lady of Nidalia (Islands of Terror), a power-hungry tyrant like Azalin or the lord of Falkovia (Ravenloft Campaign Setting) or simply a murderous monster like Harkan Lucas (Ravenloft Campaign Setting), the Dark Powers seem driven to find deliberate evil and punish it in their own peculiar fashion. Dispassionate or accidental evil does not have a history of attracting the attention of the Dark Powers, and there is no Darklord capable of communication that is not canonically shown to be fully aware of the sin(s) that lead to their damnation (some Domains have unknown Darklords, like the Nightmare Lands, or alien Darklords that may or may not be capable of meaningful communication with humanoids, such as the Elder Brain that serves as Darklord of Blutspur).
The villain in question is completely amoral – he has no issues with performing bad things, including sacrificing people in cruel ways – but he has, let's call it, a pro-ecological mind, which wants to avoid the destruction of entire world due to the event he has originally triggered.
Is there, anywhere in the lore, a way to convince Dark Powers to pull out a piece of land towards Ravenloft? Will they be swayed by 'being evil' when your ultimate motive is kind of proper? Can you think about any smart way to fool them ? (last question might be better for WorldBuilding forum, so ignore it if it is too much off topic)
Best Answer
The Dark Lords are all about punishing people. They would be considered sadistic, if they demonstrated any pleasure in administering these punishments. It is the need for punishment that drives their selection of Dark Lords.
Take Strahd von Zarovich himself...
This cycle repeats ad infinitum. The torture, the punishment, is in getting oh so close but never being successful.
In your example case, the Dark Powers would not take this person or his castle into the Dread Realms to save his home. There is no level of evil, no degree of wickedness, that would encourage the Dark Powers to make anybody's personal goals successful.
If he is truly terrible enough to earn a Dread Realm, it's entirely possible they might bring him in after his world has been destroyed. He knows it has happened, he knows it is his fault, and more importantly... he knows it will happen again. How is that, you ask? Because when they create the Dread Realm, it's just after he's taken whatever action will inevitably lead to his ruin, but before that ruin comes. And that ruin always comes... every... single... time.
That's how the Dark Lords punish people.
In truth, if you want to "bring your game into Ravenloft", the question you should be asking yourself is this:
Isn't it already there?