Yamini is without doubt the mastermind behind all this. I can give many reasons for that:
1. See Yamini is desperately trying to protect all the criminals. Why??
First she got the pandit, then guruma. Yamini has lot of knowledge about this superstitious god related stuff. So it only makes sense that she has brought the Nevla to kill the Naagins since she is the ONLY one in the family who is an expert in these things.
2. Yamini knows each and everything about Anky and co. Devdi Raaz, Mali Kaka raaz, Naagmani raaz etc. How? Ramya (Shailesh's wife) doesn't seem to have much clue!. But Yamini knows everything. So it's highly likely that she is a culprit herself.
3. Anky's coat was used yesterday by the culprit. It's ridiculous for Guruji or anyone else to go into Anky's room to get a coat?🤣
Ritik was 5 year old that time. And we ALREADY KNOW that Anky and Shailesh are culprits. So that leaves Yamini.
4. Yamini is not wearing the ring yet. She's playing a smart game. Wearing the ring will expose her identity of being a culprit. Naagin doesn't know who the culprit is. If Shivanya/Sesha had seen the ring on her finger, then she they get to know that Yamini is a culprit. So she's cleverly NOT wearing the ring. Also Ekta mata wants to make it more exciting here.
5. Yamini will mostly have an exciting back story. What's her relation to the Raja? It's clear now that Ritik is Raja's son. But who was his mother?
Were Yamini and Raja hubby-wife? Did she ditch her husband and go with Mali Kaka (bcoz of her blind love towards him) and Ritik is her own son???😆
There are endless possibilities.
6. Also the Khooni Saas (Yamini) v/s Naagin Bahu (Shivanya) fight is going to be very thrilling. A sure shot TRP gainer for balaji and colors. We can expect 6+ trps with this.!!!😃