Yama, Lord of Death, is a Dharmapala, or Wrathful Deity, and the main character in many cham dances. In his right hand, he carries a club (originally believed to be the mummified corpse of a baby) with a small skull on top.
He was a monk who was on his final hour of the final day of a 50-year long meditation to enlightenment when he was beheaded by two thieves. The monk was full of anger in his death that he felt around for his head to put back on, but mistakenly grabbed the bull's head that the thieves had earlier killed (hence the bull-like nose). He then proceeded to kill the two thieves, made cups from their skulls, drank their blood and ate their flesh and organs. Afterwards, he went on a murderous rampage until the bodhisattva Manjushri transformed himself into Yamantaka and defeated Yama, turning him into a protector of Buddhism.