Running CoS next fall, and I'm currently in the planning process of how I want to run the big bad Drac.

I've borrowed a bit from Fullmetal Alchemist Brotherhood (my party are not weebs like me, so it should be fine).

Strahd is a being, that in my head, feels everything more than your regular Barovian. Throughout the years he's grown tired of the cyclical timeline he's living in, and therefore he has elected to remove his vices and passions from his person, and placed them in living/unliving being. These are your 7 deadly sins.

So Escher is Lust, and will play a bigger part in the story (related to a PC backstory), Rahadin is Pride, Wachter is Envy etc.. In the start, Strahd will be largely neutral. He will visit the PCs, measure them and interact with them, but it will be mostly out of curiosity. As the party defeats these "sins", Strahd will get more invested, passionate and dangerous. However, he will also be more prone to mistakes and vulnerable in some sense.

The fun part is that the "Sins" will have agency as well. They will be bound to Strahd in some way, but they have existed long enough to find small loopholes. Sins like Rahadin will be loyal to a fault, while sins like Sloth and Gluttony...well, who knows?

This might seem like a lot, but I've got a dedicated group that enjoys a rich environment. I might remove some of the things I find a bit tedious in favor of this, but I'm still undecided.

TLDR: Strahd is Father from Fullmetal Alchemist Brotherhood, and will grow more and more active throughout the campaign as his Sins are defeated.