Bedrockgames
I post in the voice of Christopher Walken
It seems to me that the domain lord concept is, IMHO, the weakest concept in Ravenloft.
It is fair if you find it weak, but I honestly think the Domain lord concept is the very heart of the setting (and I would say very popular among most Ravenloft fans)
Yes, it works for Strahd, but I find it to be overly restrictive and problematic. It's quite anti-climactic if any domain lord can never be defeated.
They can be defeated. The point isn't that they can't be defeated. It is that beating one is like beating Dracula. It is a very big deal and will often take a lot of work and research. And it will be dangerous. And some are more difficult to beat than others
That's not to say that beings such as these shouldn't exist, but it's often left to the imaginations of the GM to determine what, if anything, happens to the domain if the lord is defeated. I know it's part of the shtick that the lords are often tortured subjects as well, though I'm not sure that really adds anything to the setting, really.
The idea is the domain is either going to vanish, become part of a neighboring domain, the people and the land will be freed and returned if they came from somewhere else or some stronger personality in the domain will become the new lord. I don't personally see the problem with this being determined by the GM.
Of the modules I'm planning on running, I don't know that I'm really going to lean into that concept at all, really. It seems burdensome and unnecessary to me.
In my opinion, just having run Ravenloft a lot over many years, making domain lords the focus of adventures isn't a good idea. They are important villains, they can become important and be occasional focuses of the adventures, but it is much better to use domain lords as models when creating villains (not make new domain lords but understand that what is happening to a domain lord happens to a regular monster on a much smaller scale). The best campaigns I ran were structured around monster hunts, and only occasionally would that involve a domain lord (often not as the focus of the hunt).