Millenniummon

Millenniummon (ミレニアモン, Millenniumon) is Mega Digimon in one of Ken's flashback and the second main antagonist of Digimon Adventure:.

Digimon Adventure 02
In Invasion of the Daemon Corps,

Digimon Adventure:
It was revived when Sakkakumon had absorbed the data of other Digimon to give its a new new body, when it was born of Kimeramon. But when Goldramon and Magnadramon fought it, its soul survived the battle and made it evolve into ZeedMillenniummon.