In the animated movie, Digital Monster X-Evolution, the original Digital World was cultivated and populated with Digimon by Yggdrasil. However, the continuous multiplication of Digimon left the computer unable to handle the data load, resulting in an apocalyptic event known as the "Digital Hazard" that saw the Digital World begin to collapse. Yggdrasill initiated "Project Ark," hand-picking a small number of Digimon to survive the catastrophe and transplanting them to a new Digital World it had created. However, Digimon who survived the death of the old world by way of the mysterious "X-Antibody" have appeared in this new Digital World, disrupting Yggdrasill's plans.

In Digimon Savers, Yggdrasil is the God of the Digital World. It has command over the Royal Knights.

(Source: digimon.wikia.com)