- "We have to create the ideal world that, um, the count wished for in his heart... A world of love, not war. Yeah, let's all pencil that in. An appointment...of hope."
- ― Nastasia, Super Paper Mario post-game
If the heroes go to Flopside and listen to Carson at the Overthere bar, he will tell a story called "Of Bats and Men" (the title of which is a parody of Of Mice and Men). The story talks about a man searching for a girl he loved who is missing. While he is searching, he discovers a bat in a trap and sets it free. Later that night, while the man is sleeping, a woman whom he has never seen appears to him. In the story, it is said that the bat transformed into that woman and pledged, out of love, eternal loyalty to the man. It is implied that the man is Lord Blumiere, the girl is Timpani, and the bat who transformed into the woman was Nastasia.
Nastasia was first seen in the wedding with Bowser, Peach, Count Bleck, Luigi and Bowser's troop. She uses her hypnotic magic on Peach when she refuses to marry Bowser in order to force her to agree to it. While she's initially able to resist, she is eventually forced to say "I do", which summons the Chaos Heart, which in turn, brings forth The Void that will consume all worlds, kicking off the plot.
Later on, she is seen trying to brainwash what remained of Bowser's forces to serve Count Bleck instead since it is revealed she's already done so with most of them. She also tries to brainwash Princess Peach after she wakes up in the castle after the wedding, but just as she corners her at a dead end, Dimentio teleports her away to Flipside to serve his own plans. However, she later succeeds in brainwashing Luigi into a minion of Bleck's who goes by Mr. L since Dimentio doesn't intervene, as allowing this to happens also serves his plans.
She is shown to be punctual, and ruthless according to her co-workers. She orders around Count Bleck's other minions: O'Chunks, Dimentio, and Mimi, and is ultimately in charge of Castle Bleck. She also is the one who hypnotized Luigi to be Mr. L. Her name may come from Nasty, Anastasia and Natasha (or Natalia). Once you complete the game she is over at Flopside's 1st heart pillar (World Five's heart pillar).
Conversations with Count Bleck reveal he had saved Nastasia once before, then she swore loyalty to the Count in return for his actions. As well as later on, she reveals subtly to have feelings for Count Bleck, which he dismisses; however, both Bleck and Nastasia have a deep bond, as he offers to let her leave without any punishment, to which she decides to stay due to her feelings of the Count and the debt she owes him for saving her life.
"Nastasia is Count Bleck's executive assistant. She's in charge of scheduling, organizing, and brain control. Word is, she's got a secret crush on the boss."
- Hypnosis: As seen on characters like Bowser's minions and Princess Peach, she has the ability to brainwash people. The best example for this is Mr. L.
She is the only one of Count Bleck's forces who is never fought against.