Originally posted by: Shaavi
It is true that the Guruji clearly said "khoon k badley khoon jaan k badlay jaan", because Pratap gave both. He could have killed himself on that land without spilling his blood like taking poison or something like that. But instead he kills himself by cutting his wrists making his blood seep into the ground.
When Saudamini did Tantra on Nirvaan, she clearly says that Nirvaan has to die within 7 days other wise the Tantra will backfire on her. It is the same thing with Niyati. When Niyati finds the truth regarding Saudamini, Kanchan tells that Niyati should be the next target of Tantra. And because of that she had 7 days. That is why Guruji says that whether she wins of loses, she will die because of that Tantra. Niyati takes that opportunity to free her family from Tantra before her death and accordingly makes that vow. That she will give her blood and life for the family.
Just before Saudamini comes to the basement, Niyati cuts her wrists and fulfill the part of being Pratap's daughter. It was his blood which fueled the Tantra and her blood cuts it. Since Sunaina shares the other side of Niyati's blood, she is able to sacrifice her life for Niyati's. Both Sunaina and Niyati shared part of the sacrifice in the end.