Tripindi Shradh is a special ritual performed to bring peace to ancestors whose Shradh rites might not have been performed regularly (perhaps for three consecutive years), or for those who suffered an unnatural or untimely death (like accidents, suicide, murder). It addresses ancestors from the last three generations whose souls might be lingering in an unsatisfied state (Preta Yoni). It involves invoking Brahma, Vishnu, and Mahesh (Shiva) and offering Pindas to pacify these souls.
Pishach Mochan Kund in Varanasi is uniquely powerful for this ritual. It is believed to predate even the arrival of Ganga Maiya on earth. Performing Tripindi Shradh here is said to specifically liberate souls suffering due to untimely death or those stuck in spirit-obstruction states (Pishach Yoni), granting them Sadgati (peaceful passage). The Garuda Purana and Skanda Purana mention its significance. It’s considered the primary place for such specific Shradh karmas.