Who is Haldar from Sister of My Heart and what is their importance?

Haldar is the man who tricks Gopal and Bijoy into going on a trip to retrieve rubies from a cave in the Sundarban jungle. Haldar asks Gopal for money to fund the trip. It is Gopal who asks to go with Haldar and get his own ruby. After the men get their rubies, Haldar drugs the two men in an attempt to kill them and keep their money and jewels.