6/25/20 - This is it!
Between sessions, I let the arcane trickster know that since his whip has traveled through the whole castle, has been used successfully against the Avatar of Death, and the party just got blessed from freeing the last Belmont, the whip is now a +2, and deals 1d6 fire damage versus undead and evil creatures.
Our Gloomstalker had to stay home to watch his kids and attended via Discord on speakerphone. One of the other players had it pulled up on his laptop, and would take photos of the battlemat and post them in Discord for the remote player to see. It worked pretty well.
After a short hurrah re-cap, the party heads up into the throneroom. The doors slam shut behind them with a boom, and Dracula gives a short monologue, then we roll initiative. Nobody chose to interrupt or yell back at Dracula. The throneroom is 120' x 90', with 5' marble pillars 15' off the wall at 15' intervals. There are blacked-out windows between each pillar, with curtains over them. The windows were there to provide the party with an option to cut the curtain and smash a window to let some sunlight into the room, which would create some no-go areas for Dracula. I even marked North on the map so they'd know which side to smash...nobody went for it.
Both forms of Dracula has 408hp as written, but I bumped them both to 510hp. Even so, the combat lasted 3 or 4 rounds for Dracula's first form and 2.5 rounds for his Vampire Dragon form. He regenerates 30hp per round, but there was so much radiant damage that he almost never got to use this. I had no resistances on him, and no vulnerabilities. I thought about radiant vulnerability, but one reason to skip it was simple bookkeeping...plus, you know, Lord of Shadow and Darkness and stuff.
In his first form, he got two turns per round. During both turns, he can teleport anywhere in the room as a bonus action.
In one turn, he would act as a warrior, either doing a typical claw/bite, with the bite's necrotic damage being 6d6, or he'd use his Shadow Blade for 5d8+7 damage. His to-hit bonuses were in the +13 to +14 range, so he hit with almost every attack made the whole battle.
In the other turn, he acts as a caster, and I roll off a 3-option table to see if he fires 8 Melf's Meteors, uses Charm (15' cube), or uses Fireball (8d6, leaves a Fire Elemental behind).
Warrior Dracula was super unimpressive. The party Barbarian has a helmet that grants immunity to psychic damage, so the Shadow Blade flat out did nothing on hit. Dracula tried to grapple the barbarian a couple of times to bite him, but failed. He then teleported across the room and Shadow Bladed the Paladin, but was Smote in return. Warrior Dracula ended up successfully grabbing and biting the Gloomstalker, but this was near the end of the fight.
Casting Dracula fired off two fireballs - I forgot the fire elemental for one. The fire elemental tied up the paladin for 2-3 rounds working through its 102hp. He used Charm once, hitting only the monk, who failed his save...but then used Still Mind on his next turn to negate it. He used the meteors once, splitting the damage across 3 targets and doing some damage.
Lair actions turned the room shadowy & short-ranged, which didn't imact much, summoned bats twice through the battle, said bats landing a total of about 20 points of damage over 4 rounds because a swarm with +4 to hit for 2d4 is nearly irrelevant at level 12, and then did a minor (18 point?) heal on him by draining a bit of life from everyone around him.
Everyone except the cleric (Bless, Guiding Bolt on Dracula, healing) & paladin end up contributing large amounts of damage to the Transylvanian Anti-Vampire fund, and Dracula soon is down to 0, at which point darkness swirls around him. I play an evil devil laugh that gets really deep on my phone, followed immediately in the playlist by a dragon roar, and it's now Vampire Dragon time. The barbarian eats a full attack including a claw crit and a bite (which reduces max HP & heals Dracula some) and is brought below half, but thanks to resistances, is still standing. The monk runs over and does damage, while the gloomstalker backs off and does archery, and the Paladin finishes off the fire elemental. The arcane trickster moves closer and has his familiar use Dragon Breath (cast earlier) to do like 18 points of fire damage.
Dragon Dracula uses his legendary wing attack to fly over to the door right before his turn (knocking two characters prone for minor damage), and then fires off his breath attack, hitting 4/6 party members and the familiar. 18d6, 66 necrotic damage, Con DC 21 half. Two party members go down at 0hp, but the cleric's Channel Divinity brings them right back up. The cleric also threw a Heal in there at the barbarian for 77hp of healing somewhere in there, which must have been before the breath weapon. Everyone piles onto Dracula, taking tail attacks in retaliation (legendary actions), but ultimately killing him before he can take another turn. The Gloomstalker gets in the final hit, and he dies in a burst of shadow.
Overall, Dracula was less threatening in terms of player kills & TPKs than Death was, but he was still no pushover, and lasted for about 6 rounds. I'm pretty happy with how it went, although I may give him a better choice of Legendary Actions, as "move around the room or make a melee attack" options were not useful when nobody was next to him and he didn't want to be next to anyone. He didn't have to be a super-death-hard battle, as long as he was a good tough fight that FELT like a tough Dracula fight... and I think it did.
The party quickly loots the Crystal Ball of Truesight (next to throne), the +2 Breastplate, and the Ring of Fire Elemental Control, and then the castle starts shaking under them before the AT can get very far with ritually casting Identify. They are 150' up in the central keep and need to get down. The solutions are:
-AT Spider-Climbs with the Gloomstalker on his back
-Cleric Feather-falls (thanks to shield) with the Paladin holding on
-Monk Slow-falls
-Barbarian jumps out the window and rages before hitting the ground; Arcane Trickster casts Web to cushion the landing.
Then they run 300' across the roof. I make some rolls for "castle disappearing under you as it phases into the Plane of Shadow", but all that happens is the monk (fastest party member) has a stone disappear under his foot, then phase back in, dealing 5 force damage. They then have to go 100' down again to get down the castle wall. Same solutions as before, except the Barbarian climbs. The wall briefly disappears under him, and he falls the last 20'.
The party then walks down the road away from the disappearing castle, enjoying the sunshine and seeing things return to normal.
What do they do next?
Everyone hits level 13. They are all fabulously wealthy, about 8 levels higher than almost anyone else in Europe, and being super-famous as the people who killed Dracula.
They decide to form "The Belmont Order" in honor of the vampire-hunting family, and build a manor, village, and training academy right where Dracula's castle was. They will train monster hunters and become a regional military power, as well as building a temple (cleric) and will help to restabilize and repopulate the devastated countryside. This will include a large library, alchemist's lab, and fortified underground areas.
Dmitri the Barbarian will go home...he rolled for "this is your life" in Xanathar's during the session, and decided that he'd been exiled from his dwarfhold for 100 years, so he went back to see his family that he hadn't seen in 100 years. It's pretty vague, but returning as famous, wealthy, and super-powerful generally grants success in resolving old issues like that. He takes the scenic route across eastern Europe with his wife and adult children, doing some adventuring on the way back to the Belmont Order, returning after about a year to live there.
Reybella the Cleric will help heal the area, build the temple, and adventure with Ratel (their characters aren't married, but the players are).
Ratel the Monk will finish reading his Stat tome, do some adventuring to clean out the monsters in the region, and will learn how to ride and handle horses. He will also take on some monk apprentices later.
Malcolm the Ranger will oversee construction of the Belmont Order facilities and training grounds. He will also help find the captives that the party freed, and see if some of them will come back to settle around the new Order.
Adrian the Arcane Trickster will run the Belmont Order, and will study alchemy & monsters. He wants to upgrade his chain whip with holy water, and he wants to redecorate his obviously-drow Spider Armor to be less drow-like.
Teador the Paladin will go home and break the news to his brother's wife & kids that Adrian the Sorcerer is dead. He will give them his brother's Wand of Lightning, and will later return to the Order. He will work with whichever military he was with to build an organized military force around the Belmont Order to give is some organized punch.
And that's what everyone does for the next 5+ years. I have copies of everyone's level 13 character sheets, and we may see a sequel campaign in a year or two real-time.....