The Demonic Spirit



The Demonic Spirit is an unnamed, mysterious, malicious, and extremely powerful being who devours souls.

Biography
The origins of this creature are unknown, but it seemingly devoured countless victims, the latest being Kuni's family. After capturing them, the monster kept her alive and forced her to lure in more victims for it to devour. She was crying in the woods, when Jack met her she ran back in the house causing Jack to follow.

After Jack investigates the house, the demon finally reveals itself, but despite Jack's best efforts, the demon gains the upper hand and consumes Jack's soul. An intense battle ensues inside the demon's own real form, which Jack eventually wins, destroying the monster in the process and freeing at least some of its victims.

When Jack returns, Kuni is reunited with her family, as the demon's curse on her house has been lifted.

Trivia

 * This creature is one of the few antagonists that has no affiliation to Aku in any way. It can also be considered the most malicious and terrifying enemy Jack has ever faced, even by Aku's standards.
 * Many fans and even the creators consider "Jack and the Haunted House" to be the scariest and most disturbing episode in the entire series.