I just watched Horror of Dracula. It's a fun movie, but a bit slow, and it could use a lot more Christopher Lee and less rambling monologues by Peter Cushing.
As I watched, I was impressed by a few things. His castle was very nice and tidy, and he even had pineapple available for Harker on his arrival. Dracula is definitely up for a Good Cryptkeeping award. He's got a pretty nice travel-coffin as well. This Dracula likes luxury. He's also got a barely contained fury under his veneer of civilization. His fight with his "bride" early in the movie is my favorite part. There's nothing civilized there - just two killing machines facing off over Harker's oh-so-delicious blood.
So, naturally, my thoughts turn to the megadungeon. What place is there for a vampire in the Anomalous Subsurface Environment? The answer is easy - the lower levels. They've got too many hit dice for level 1. Duh.
I don't plan to just have any old wanna-be vampires in my dungeon though. If I'm going to place an iconic monster like that, I'll stick to the best. Dracula himself! Specifically, the savage blood-drinking hell-beast who wears a thin veneer of civilization, but casts it aside whenever it is mildly inconvenient. Unbridled rage is his natural state. He'll of course have his three brides with him, and maybe a "Lost Boys" contingent of recently turned adventurers.
Detailing his lair isn't really necessary right now, that's many many levels down. He'll have been interred for several thousand years at this point, and bored out of his undead mind. Oh, the fun he'll have as rumors of surface-folk invading the dungeon trickle down to his lair. He'll also have fresh pineapple waiting. Not sure how yet, but he's an excellent host when he's not tearing your throat out. He'll find a way.
I like using iconic creatures like Dracula because they don't require a lot of definition to communicate mood to the players. "Count Toothula", or any other vampire I came up with myself, wouldn't carry nearly the same emotional and intellectual freight as Dracula. Name drop that guy, and the party is going into full paranoia mode, and presumably doing their best to never accidentally stumble across his lair.
That's the same reason I drop in things like the Church of Starry Wisdom. The players (some of them, at least) are going to know what that means, and it saves me work on building mood and suspense. It would be an absolute cheap trick in a literary work, but this is a game, not literature. Anything that makes the dungeon more fun is fair play.