Human Spirit of Water
The Human Spirit of Water (水のヒューマンスピリット, Mizu no Hyuman Supiritto) was created from Ancient Mermaimon after her battle with Lucemon in the past. From there it passed to Cherubimon's keeping. When Cherubimon betrayed the Digital World he transformed it into Ranamon. When Ranamon is defeated by Izumi in "Ranamon's Tenacity! Female Digimon Personal Combat" it is trapped inside her D-Scanner until she gives it to Kouji in "Spirits Become One! Takuya and Kouji's Ultimate Evolution!" to allow him to hyper spirit evolve into Magna Garurumon.
(Note: Is called Spirit of Water H in the TCG.)