Kid (IDW)

The Demon Child is a supernatural entity that exists in the afterlife that Oroku Saki experienced. His name and nature are unknown, as is whether his word can be trusted.

He first appeared to Saki when he first arrived in the afterlife and confirmed that unlike the regular residents of that place, the ninja was only passing through. However, the Demon Child then warned Saki not to disturb the natural order of the afterlife.

Saki ignored the child's warning, and went on to enlist an army of dead warriors to charge on a castle. After he slew their king, the Demon Child reappeared to reveal that the king was himself an older Saki. He then predicted Saki's future: that he would lead armies and conquer the world, then destroy it and remake it; wipe away humanity and build a new world full of barbarians and mutants; and eventually die and become the old king, only to be slain by his younger self. The Demon Child seemed to be amused by this prospect.