Kan Gha Roo

A warlord from the Underland, and apparent follower of Orcus, Prince of Undeath. Jack's mother and maternal aunt were dead and buried, but Kan Gha Roo invoked dark necromantic powers of Orcus to raise them into twisted unholy mockeries of life.
Kan Gha Roo and his men captured Jack and his siblings. They killed Hides Bushtucker and Jack's own undead mother forced him to pluck the eyes out of his brother's head. They were locked up, but a mysterious man seemingly from within Kan Gha Roo's men helped them escape. They killed - or rather, destroyed, as she was already among the undead - Matilda, Jack's own aunt and his mother's sister, on the way out.
Even once they escaped, they were pursued. Jack tried to hold them off as long as he could so that his sisters could get away, but got knocked out in the ensuing scuffle. He awoke not knowing where they were, but being told by his apparent saviors that they were safe.
Unfortunately, even as Jack boarded a boat, he received a note that Kan would continue looking for him and his sisters.
Later, when Sam Fatts' Crew went to trade The Time Machine back to Redfoot the Relentless, Kan Gha Roo and Alyssa were lying in wait with some underling bandits. When Kan Gha Roo and Alyssa realized they were outmatched, they retreated, but left two bandits to get captured by Jack.
Once they got on the boat and counted the money, Redfoot possessed Sam once more and said that his business with Kan Gha Roo was done now, and he could honor the new deal he had made with Jack to find a way to contact Valhalla. He has yet to explain what the deal with Kan Gha Roo was.