St. Andral's Feast

The Setup

About three weeks ago, a young woman came to town, someone that a few in the town recognized. She spent only a few days in town, speaking with one of the church orphans in the bar, and speaking to the coffin maker as well. This woman was Nthanda, Strahd's protege. She paid Miroslav to steal the bones of St. Andral, and smuggled them, along with six vampire spawn, into the coffin maker's shop by paying him a handsome fee.

The Events

The players can lessen the impact of this event from occuring by returning the bones of St. Andral to the church or by destroying the vampire spawn hiding in the coffin maker's workshop. If they stay in Vallaki for more than three days and do neither of these things, then the worst version of events occur.
On the fourth afternoon, Rahadin will arrive in Vallaki and set the events into motion. He will go to the town square and will make a loud announcement during the festival that the burgomaster has not paid the required taxes in several many months, and the Lord's patience is at an end. He will do nothing at this time, but this will rile up the people (and occurs shortly before the Tiger, Tiger event.) The festival will fall into chaos, and the burgomaster will resort to setting the town's guard on the people to shepherd them back to their homes.
If the players failed to return the bones and/or did not kill the vampire spawn, the following events also occur: on the fourth evening, Nthanda will arrive at the coffin maker's workshop, and will release the vampire spawn, with instructions to assault the church and the evening congregation. If the spawn are killed, she will go directly to the church. The spawn will climb up the outer walls of the church (if they are alive), while four swarms of bats will swarm into the church, terrifying the congregation into fleeing the church into the waiting claws of the spawn. 2d6 adults and 2d6 - 1 children will perish in the attack, including all three of the orphans who lived in the church.
Within the church itself, Nthanda will enter in bat form, then revert to vampire form to attack Father Lucian. Unless the players intervene, he will kill him easily and return immediately to Castle Ravenloft. If Father Lucian dies, the locals will bury his body in the church cemetary, where it will rise the following night as a vampire newborn. If Rictavio learns of the priest's fate, and the party has met him, he will suggests that the players burn the priest's body to ensure it doesn't rise from the dead.

Development

If the players fail to kill the vampire spawn or return the bones of St. Andral, then after one day, the surviving townsfolk will march on the burgomaster's mansion. Without the players' intervention, the mansion will be set ablaze. The baron, his wife, and his natural son will be dragged to the town square, thrown in the stocks, and stoned to death. Izek will flee the town to avoid the same fate. Lady Fiona Wachter will take control of the town.
If the players manage to avert the worst of the crisis, then Strahd will task Nthanda to deliver a letter (Strahd's Invitation) to the party.

Homebrew

Vampire Base CR: 3

Small to Large undead, any

Armor Class: 15 (natural armor)

Hit Points: 55 (7d8+24) 7d8+24

Speed: 30 ft

STR

16 +3

DEX

16 +3

CON

10 +0

INT

10 +0

WIS

10 +0

CHA

16 +3

Saving Throws: Dex +5, Wis +2, Cha +5

Skills: Perception +2, Stealth +5

Damage Resistances: Necrotic; Bludgeoning, Piercing, and Slashing From Nonmagical Attacks

Senses: darkvision 60 ft., passive Perception 13

Languages: Any it knew in life

Challenge Rating: 3 ( 700 XP)

Proficiency Bonus: +2

Regeneration. The vampire regains 10 hit points at the start of its turn if it has at least 1 hit point and isn’t in sunlight. If the vampire takes radiant damage, this trait doesn’t function at the start of the vampire’s next turn.
Spider Climb. The vampire can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Vampire Weakness. The vampire has the following flaws: Forbiddance. The vampire can’t enter a residence without an invitation from one of the occupants. Staked. The vampire is destroyed if a piercing weapon made of wood is driven into its heart and its mouth while it is incapacitated in its resting place. Sunlight Hypersensitivity. The vampire takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.

Actions

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one willing creature or a creature that is grappled by the vampire, incapacitated, or restrained. Hit: (1d6 + 3) piercing damage plus necrotic damage. The target’s hit point maximum is reduced by an amount equal to the necrotic damage taken, and the vampire regains hit points equal to that amount. The reduction lasts until the target finishes a long rest.
Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: (2d4 + 3) slashing damage. Instead of dealing damage, the vampire can grapple the target (escape DC 13)
Charm. The vampire targets one humanoid it can see within 30 ft. of it. If the target can see the vampire, the target must succeed on a DC 15 Wisdom saving throw against this magic or be charmed by the vampire. The charmed target regards the vampire as a trusted friend to be heeded and protected. Although the target isn’t under the vampire’s control, it takes the vampire’s requests or actions in the most favorable way it can, and it is a willing target for the vampire’s bit attack. Each time the vampire or the vampire’s companions do anything harmful to the target, it can repeat the saving throw, ending the effect on itself on a success. Otherwise, the effect lasts 1 hour or until the vampire is destroyed, is on a different planeof existence than the target, or takes a bonus action to end the effect.
Children of the Night (1/Day). The vampire magically calls 2d4 swarms of bats or rats, provided that the sun isn’t up. While outdoors, the vampire can call 3d6 wolves instead. The called creatures arrive in 1d4 rounds, acting as allies of the vampire and obeying its spoken commands. The beasts remain for 1 hour, until the vampire dies, or until the vampire dismisses them as a bonus action.