World Tree

«Yggdrasil» is the massive tree that is at the center of ALfheim Online. The name "Yggdrasil" in Norse mythology means "World Tree", which connected the nine worlds in Norse Cosmology. It was said that the first race to reach the legendary city, floating above Yggdrasil, and have an audience with Fairy King Oberon, who lived there, would be reborn into true fairies, the ALF.

The hover limit imposed on the system would be eliminated and unlimited flight would become possible. Along with it, the successful race would be capable of becoming rulers of this infinite sky. It was said to be possible to enter this floating city through a dome at the root of Yggdrasil.

However, Kirito later discovers that there is no city above the World Tree. Also, Yui claimed that the number of guardians that defended the World Tree was too high, meaning that the Grand Quest was, in fact, never intended to be possible to be completed. This is further backed when Kirito finds that the gate at the top of the tree couldn't be opened by players as it was locked by administrator codes rather than a quest flag.

ALfheim Online
Kirito attempts to climb the World Tree on two occasions to rescue the captive Asuna from Fairy King Oberon. The first, a failed solo attempt and the second with Leafa, Recon, and the Sylph and Cait Sith raid squadrons which was successful. However once Kirito reached the gate he found it locked by administrative codes, Yui determined that the gate was never intended to be opened by players. However, Kirito is able to open it by having Yui use the coding from the admin card Asuna dropped from her cage.