The God of the Digital World and leader of the Royal Knights.
Yggdrasil has made multiple appearances throughout the Digimon franchise. It's most notable appearances in Digimon X-Evolution, as the main villian and in Digimon: Data Squad as commandeer of the Royal Knights.
Also seems to have a tendancy to be rebelled against, by Alphamon and Omegamon in X-Evolution and Omegamon speaking for all of the 10 present Knights in Data squad.
In Digimon World Dawn/Dusk, Yggdrasil is mentioned by Grimmon, implying that he intended to become a more powerful god than it.
Seraphimon also hinted to Yggdrasil along with Digimon X-Evolution in Digimon World 4 when asking about why LordKnightmon was on the side of Mecha Rouge X. He wonders if the Royal Knights and the Mecha Rouge are working together, but decides against it, saying that's ridiculous. Truth is, if this game is based off X-Evolution and possibly Chronicle as well, that probably IS what's happening, with Mecha Rouge X being an expy of Death-X-Mon.
The eight Digimon film which was made in CG by Imagi Animation Studios. The Digital World had become so overpopulated that the super computer, Yggdrasil ...