Divyachini took dristi's blood to get back her powers in last episode.may be she was able to complete all rituals tht might be d reason of drishti's pain
I think the pain is coz of the twin connection of being twins and having divided parts of a single gem in them.
I wonder if Pi's tantra will work, coz Shikhu was shown in Pi's adda after Pi Bi left, leaving the ashes on the piano unprotected. Shi might have replaced the ashes.