Looks a fair start. The AC19 seems right.
So, shall we start on the special abilities? Going by Molday's description, we want:
A) "knock on door and kill" special attack
A variant of
finger of death they can use once per night that does not need line of sight? Will save rather than Fortitude, since they must resist answering the call? No, I've got a better idea - we'll model it on
phantasmal killer. Something like:
Call of the Dead (Su): Once a night, a vrykolakas can call out the name of a sapient creature within 200 feet. That person must make a DCX Will save to resist answering the call. If they fail, they will die the next day (roll randomly to determine the time) unless they succeed at a DCX Fortitude save. This is a sonic, fear and mind-affecting power.
EDIT: I've thought of some tweaks to the above, I'll lay them out in my next post.
B) The "Sit on Sleepers and Oppress Them to Death (creates another Vrykolakas)"
That sounds like a combination of the Night Hag's Dream Haunting and Create Spawn.
Oppress Sleeper (Su): Once per night, a vrykolakas can sit upon a sleeping creature, causing agonizing nightmares of a horrific presence crushing them under its oppressive weight. The victim gets no benefit from their night's sleep, and takes 1 point of Constitution drain. Any humanoid slain by Oppress Sleeper rises as a vrykolakas the following night. Such vrykolakas are under the command of the vrykolakas that created them and remain enslaved until its death. They do not possess any of the abilities they had in life. At any given time a vrykolakas may have enslaved vrykolakas totaling no more than half its own Hit Dice; any spawn it creates that would exceed this limit are created as free-willed vrykolakas.
C) "Can only be killed by exorcism or digging up and burning their corpse"
Give it fast healing like a vampire (including the turning gaseous and returning to its grave if destroyed), although they don't have at-will
gaseous form like regular vamps. Then note that consuming their body with fire or exorcism destroys them. I guess we should do them separately.
Fast Healing (Ex): A vrykolakas heals 5 points of damage each round so long as it has at least 1 hit point. If reduced to 0 hit points in combat, its body dissolves into invisible vapour (as per the invisibilitygaseous form spells) and flies directly back to its lair. Any additional damage dealt to a vrykolakas forced into gaseous form has no effect. If it cannot enter its lair due to a protection from evil effect or the like, it travels to the nearest similar spot such as an open grave, the cellar of an abandoned house. Once it reaches its destination, the gaseous form ends and the vrykolakas resumes corporeal form. The vrykolakas is then helpless for the next hour, then is no longer helpless and resumes healing at the rate of 5 hit points per round.
If the vrykolakas is burnt to ashes (-10 hit points or less) while it is resting as a corpse during the day, or after it has been rendered helpless as described above, it is permanently destroyed. plus
And the exorcism:
Vulnerability to Exorcism (Ex): A vrykolakas is permanently destroyed if an exorcism or similar spell is successfully cast upon it, decaying into dust and bones within a round.
C Growing in power until they become Greater Vrykolakas
Do they just need time for this, or should we have them gain Hit Dice as they kill victims / create spawn / drain energy levels, becoming Greater Vrykolakas when they hit 13 Hit Dice?
At the moment I favour the Create Spawn route, we could add the following to Oppress Sleeper:
A vrykolakas gains 1 Hit Dice for every vrykolakas it creates with Oppress Sleeper. When it reaches 13 Hit Dice it becomes a Greater Vrykolakas.
Let's see, that means it needs to kill & tranform six people to become a greater vrykolakas. Assuming they're healthy Greek peasants they'd have 12-13 Con, so at 1 Con a night that would take 72-78 nights, which would fit with the 80 day timeframe of Molday's description. It also matches with the "The great vrykolakas is usually accompanied by 1-6 ordinary vrykolakas under its control" bit, if this reflect how many it created before becoming Greater.