Many stories are told of the origins of Anastasia, some say she used to be a beautiful Queen who sought the Blood Kiss so as to never age, some that she was the favored general of Neferata herself turned to serve eternally, still more that she was a thief who stole the secret from Nagash himself!
Anastasia keeps quiet on the matter herself for it suits her purpose that none know the truth - she was just a common soldier, given the kiss along with dozens of others in order to put up more resistance against the Chaos invasion in order to buy her Sire time to escape.
However, she has always been a survivor and managed to escape just barely with her life. Over the following centuries she did her best to try to learn to control her new powers, but without a teacher she has still has an imperfect mastery of some. This is most apparent in her inability to grant the Blood Kiss to males without them rapidly degenerating into beastial Varghiests. For this reason all of her close advisors and lieutenants are female.
In recent years Anastasia has made her home in the ruins of an old Chaos fortress that fell to infighting centuries ago. Such was the fel magics used when it fell that surrounding area has turned into a fetid diseased swamp, shrouded in such deep mist that it never gets brighter than a haunting twilight.
Her closest advisor, and leader of the Maidens of Fens (a group of fearsome Blood Knights) is the Lady Mariska. She has been seen at Anastasia’s side only recently but seems to have already earned the trust of farour of the Anastasia.
Keeper of her menagerie and chief court wizard is Zoltan, the Withered. He is responsible for ensure that both Darda’il (her Zombie Dragon) and Terrorgheist are kept in top fighting condition.
In order to survive Anastasia has learnt not to be picky about what forces she will work with - after all is it worth risking eternal life for the sake of appearances? This means that there have been reports of her working with many many groups in order to further her aims, most recently a force of Stormcast Eternals seeking to destroy a nearby band of Nurgle demons.
In the last couple of months Anastasia has heard the summons of the Lord of the realm of Death, Nagash himself who is rallying his armies after his rebirth. She is determined that she will not just be a pawn in his schemes though and has (perhaps foolishly) sought the aid of Neferata in order to not be ignored as insignificant. To that end she is trying to increase her personal army and influence.
Her current plans are focused on gaining the loyalty of local Ghoul King, Janós the Golden, reputed to have so much wealth he dips his claws in gold before each battle. If she can gain his followers then she will be strong enough to be able to expand and teach all to fear the name of Anastasia the Scourge of the Twilight Fens!
A point to me as well