PRAYAGRAJ, India — The holy man had seen a lot in his day. It was evident in his long, white beard and naked, skeletal frame.

The ascetic, Naga Baba Prayagrajgiri, had twice before joined the throngs of Hindu worshipers who flock to Prayagraj every six years to pray and bathe at the confluence of India’s great rivers — two of them worldly, the third divine.

Over the years, he has seen the pilgrimage, known as the Kumbh Mela, swell from tens of millions of people to hundreds of millions — the largest religious gathering in the world.

But this year’s festival — the biggest and most expensive ever — was different, Mr. Prayagrajgiri said.