Jatāsura (जटासुर) was a Rakshasa who disguised himself as a Brahman and carried Yudhishthira, Sahadeva, Nakula, and Draupadi. He was overtaken and killed by Bhima.
According to the Mahabharata (Book III: Varna Parva, Section 156), Jatasura used his powers of illusion to appear in the guise of a Brahmana to the Pandavas. His objective was to gain their confidence in order to seize their weapons, ravish their wife Draupadi, and take some captives. He lay in wait "like unto a fire covered with ashes." One day when Bhima was gone, Jatasura took on a monstrous form, seized the weapons and Draupadi, and fled with three of the Pandavas, including Yudhishthira, as his captives. Yudhishthira, however, confused him by showering him with moral accusations, and Jatasura slowed down enough for Bhima to catch up. The doomed Jatasura fought valiantly, but in the end Bhima knocked him out with a punch to the neck, lifted him up and dashed him to the ground, and severed his head from his neck.
See also 
- Dowson's Classical Dictionary of Hindu Mythology