Hidimba was a human-eating demon. When the Pandavas rested in his area, he wanted Hidimbi, his sister, to catch them. Hidimbi fell in love with Bhima, who killed Hidimba and married her. Their son was Ghatotkacha.
For the story visit
http://hindumythologyforgennext.blogspot.com/2017/08/gatothgaja.html