Moon=Millenniummon

Moon=Millenniummon is an Evil God Digimon whose name and design are derived from "-Millenniummon". It is a soul Digimon that exists within Millenniummon's inner world. As a result of Millenniummon's dark spirit becoming a Digimon, it does not possess a fixed form, and although it often takes the shape of a crystal, it seems that the hatred and anger it feels against those who oppose it cause it to change shape. As it is a soul and does not have substance, it is immune to physical attacks. To defeat Moon=Millenniumon, one must first defeat Millenniummon, its true form, but it's likely there are virtually no Digimon who are up to that task; even if Millenniummon is somehow defeated, it is said that Moon=Millenniummon will separate from its now-dead physical form and be revived throughout time and space.

Digimon Adventure 02: Tag Tamers
Moon=Millenniummon digivolves from MetalGreymon in line 37.

Digimon Adventure 02: D-1 Tamers
Moon=Millenniummon is the final boss of Digimon Adventure 02: D-1 Tamers, as well as a playable Digimon.

Digimon World Data Squad
Moon=Millenniummon apears as a boss in the Dark Area, after its defeat, you will obtain the Red Jewel.

Digimon World Dawn and Dusk
Moon=Millenniummon digivolves from Kimeramon. Kimeramon must be in level 66 or higher, spirit must be 370 or higher and you must have or had a Millenniummon. Moon=Millenniummon is one of 3 opponents in the Silver Rank battle.

Attacks
 * Death Crystal: Performs an incorporeal attack that is said to chop up the opposing Digimon's spirit.
 * Dimension Destroyer