I have been doing some research on them. There are plenty of sources regarding their methods of murder and theft, but not much regarding their religious practices and what thread really held the different bands together. I am also quite confused as to how the locals did not speak out against the thuggee or how local rulers tolerated them before the arrival of the British. Can someone please explain this to me?
The religious aspects of Thug are somewhat exaggerated by legend. Kali was a kind of equivalent to an equivalent to the Patron Saint of a Guild of tradesmen for the Thugs. The bands were held together by ties of kinship. They operated away from home so did not antagonize their immediate neighbours, and there is at least some suggestion that they also bribed their neighbours with a share of the loot. Local rulers did not tolerate Thugs there was just not much they could do about them. The British East India Company became involved because their Indian soldiers were frequent victims when they were travelling alone on their way home with large sums of pay on their persons. The East India Company had the resources to launch a large scale investigation, which eventually eliminated the problem. My source Mike Dash's Thug: the true story of India's murderous cult (Granta, 2005) A review of the book I wrote for a British newspaper is here