Corrupted Human Spirit of Darkness
The Corrupted Human Spirit of Darkness was the spirit left by Ancient Sphinxmon.
Cherubimon corrupted the Human Spirit of Darkness and forced it on Kouichi changing him into Duskmon. When Duskmon is defeated the spirit is trapped inside Minamoto Kouji D-Scan until Kouichi comes to realize that the spirit and himself were not inherently evil, after which it is released and purified back into the normal Human Spirit of Darkness.
(Note: Is called Spirit of Darkness H in the TCG.)