The shape shifter was someone who knew Aryaman could be a truly powerful ally to Naagin if she somehow survives so they took his form to stab her to sow seeds of discord . It could very well be Bharni , who was absent in that scene.
Yes Bharni being that possible shape-shifter can't be ruled out bcoz she's a Naagin too but then it raises 2 points-
1-Why didn't she have her mom Uttara from a possible death?
2-Why didn't she make any effort to finish the whole Suri family then and there itself?
And if Bharni knew that Aryamaan could be a future ally for Ahana then why take Aryamaan's form to stab Purvi-she could have taken other disguises too.
I don't think it was Bharni yet I don't deny that it could possibly be a shape-shifter let's say either a shape-shifting dragon or any other supernatural creature who's in league with the Suri criminal empire.
As far as Aryamaan is concerned then Bharni might be partly right too of the curse of Naagin's love for a human being bcoz who knows Aryamaan might do a Katappa on Ahana in the end if not now for the Naagmani.He's neither innocent like Ritik nor logical like Maahir to ever have any growing attraction for Ahana.
And if Aryamaan arrived at the exact moment today like when Ahana was just killing off Rishabh then this possiblity can't also be ruled out that perhaps he was really present on the scene that day when the whole Suri family attacked Purvi's family.
If the shape-shifter knew that Aryamaan could be an ally then he probably could have known of the secret of Purvi's birth too.And it can only be possible if the shape-shifter has some kind of a future prediction power or that creature might be in possession of an ancient book which predicts future events like the one Naagins have in their Naag-Mandir.
Aryamaan could be just a normal positive guy also but him being a guy with hidden intentions makes him more interesting than just a cynical positive guy.
Maybe by the time she saw them Uttara was already dead and so was most of her family . She saw Ananta running upstairs to find Aryaman ( who was probably away from the wedding venue already , sipping alcohol at Radhika's place and moping predictably lol. ) so she took her form to give her a death as she knew she could come back as naagrani if she really has powers . She did that to ensure she started hating the man she's fallen for.
That's the only motive I could think of. Maybe she already had other plans to isolate her from all possible allies so that she solely relies on her and become dependent on her and trust her blindly. Rn, she's practically no one except Bharni by her side.
It could be Vikram too , who's probably a shape shifter himself even a naag so he stabbed her in guise of Aryaman and later found her and befriended her in pretext of being in love with her so that he can reach the naagmani or some other motive.
It could be Radhika too as she's a shapeshifter as well. Her roles and motivations will be further clear post her entry only. For now, she's a mystery card.
Or could be an entirely new person who's behind the veil until now like Meghnaad.
Also, that person had to have known Purvi won't die and come back as Ananta or else if the sole motive was to kill her off why take the trouble to take another form ? Just kill her in their original form na !

)...something was off when ananta was blaming aryaman for the gruesome killing of her adoptive family...

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