Fan:Bronze and Cobalt/Yggdrasill

Yggdrasil is a Universal Digimon claimed to be from an alternate universe unknown to mankind. She is one of the first Digimon whose level is Omni, which places her above everything else in the Digital World. Her's power is said to be so immense she is capable of wiping out the Digital World in a second. Nothing but Gaiamon himself can stand up to her power. Having all the powers of Alphamon and Omnimon, it is sometimes called the "Alpha and Omega" for her god-like power. It's overall appearence is based on her design from Data Squad, with before the battle she is shown as a sphere similar to how she is in X-Evolution.

Digimon World: Bronze and Cobalt Versions
Yggdrasil is a secret boss that can only be fought and obtained after having befriended Torodramon, Kentrodramon, Euoplodramon, Argendramon, Utahdramon, Alberdramon, Iridramon, Giganodramon, Brondramon, Cobaldramon, and Jadedramon. One can bypass befriending all of those by instead obtaining the password Digimon Fracktamon, Shaddreamon, and Goddreamon, which will allow you to skip the others and unlock Yggdrasil to battle. However, to obtain her you need to have the other Digimon mentioned anyways.

When obtained she is a Balance type Digimon specializing in all the Elements in the game, not favoring one over the other. She has no personality trait of any kind and cannot be put in a DigiFarm or be used to breed for DigiEggs. Her stats are already 99,999 HP and MP with 9,999 in every other stat when obtained, immediately making her useful due to both good attack moves and support abilities. However, her signature trait, while it can heal all nearby allies, makes them more vulnerable to attacks. She is banned from random online battles and can only be used under special rule sets that allow Digimon of her power to battle. How it digivolves into Terranadramon is yet to be revealed.