Saw an interesting book in the shop the other day; Thug: The True Story of India's Murderous Cult by Mike Dash.
I have encountered them occasionally in popular culture including the film Indiana Jones and the Temple of Doom, but always thought they were fictional, until now.
The Thuggees were considered, depending on the researcher; either as a cult or a network of secret fraternities, rather like the Rotary Clubs of today I suppose.
They are fairly old, existing in India and operated between the 17th and the 19th centuries, although some claim that they existed from as far back as the 13th century.
The Thugs worked by befriending travellers and then ritually murdering them; strangling them with a yellow scarf to the accompaniment of music and included the consecration of a pickaxe and the sacrifice of jaggery. The pickaxe was used to dig the graves of the victims.
The Thuggees were said to be worshippers of the goddess Kali and were stamped out by the British.