World Tree

The «World Tree» (世界樹), known as «Yggdrasil» (イグドラシル) in ALfheim Online's lore, is the massive tree growing at the center of the land of Alfheim.

Norse Mythology
In Norse mythology, Yggdrasil is an immense ash tree at the center of the Norse cosmos, connecting Niflheimr/Niflheim (the realm of ice and mists), Jötunheimr/Jotunheim (the homeworld of the giants (Jötnar)), Álfheimr/Alfheim (the homeworld of the elves (Álfar)), Miðgarðr/Midgard (the realm of humans (Menn)), Ásgarðr/Asgard (the home of the Æsir gods), Vanaheimr (the home of the Vanir gods), Hel (the world of the dead), Svartálfaheimr (the homeworld of the dwarves or dark elves), and Múspellsheimr/Muspelheim (the realm of fire) - the nine worlds in Norse Cosmology. The name "Yggdrasil" in Norse mythology means "the ash tree of the horse of Odin", where "drsail" means "horse" and Ygg means "The Terrible One", another name for Odin.

The tree grows out of the Well of Urðr (Urðarbrunnr), where three female divine beings, Urðr (past), Verðandi (present) and Skuld (necessity), collectively called the Norns, live and keep the tree watered. There the Norns also shape destiny by carving runes into the trunk of Yggdrasil or by weaving destiny like a web or tapestry. However, time in Norse mythology is considered as cyclical, instead of linear, and the destiny set by the Norns is not final and can still be changed by the individual agency of all living beings. Aside from the Well of Urðr, two supporting roots reach out to two more wells, Hvergelmir in Niflheimr, where the wyrm Níðhöggr gnaws at the root of the tree, and Mímisbrunnr in Jötunheimr.

In the upper branches of the tree lives an unnamed eagle, which constantly quarrels with wyrm Níðhöggr, while a mischievous squirrel Ratatosk presumably keeps the conflict going by carrying malicious messages between the eagle and Níðhöggr.

The First Grand Quest
It was said that the first race to reach the legendary city, floating above Yggdrasil, and have an audience with the Fairy King Oberon who lived there would be reborn into true fairies, the ALF. The hover limit imposed by the system would be eliminated and unlimited flight would become possible. Along with it, the successful race would be capable of becoming rulers of the infinite sky. It was said to be possible to enter this floating city through a dome at the root of Yggdrasil.

Urðr's Spring
The thickly huddled roots of the World Tree once reached Urðr's Spring in Jötunheimr without spreading. Due to the blessings of the World Tree, the world of Jötunheimr was covered in beautiful water and greenery and the Rock Giant Tribe lived in Jötunheimr with the Beast-type Evil Gods in harmony. However, once upon a time, the king of the frost giants in Niflheimr, named Thrym, transformed into a wolf and infiltrated Jötunheimr. He then stole the Holy Sword Excalibur, forged by the blacksmith god Völundr, and threw it into Urðr's Spring at the center of Jötunheimr. The sword severed the thick roots of the World Tree in the spring and, at that moment, Jötunheimr lost the blessings of the World Tree, becoming a desolate world of frost. The water of the Urðr's Spring froze and was pulled up by the shrinking roots, thus forming a bottomless pit, the Great Void, where Urðr's Spring once was. The frozen water became a huge mass of ice, with Excalibur stuck at the bottom-most part, and pierced into the crust of Alfheim.

Thrym and his subordinates then invaded Jötunheimr from Niflheimr, capturing and imprisoning the previous residents of the world, the Rock Giant Tribe in the various fortresses and castles they had built. Thrym also fashioned the large mass of ice into a linear dungeon-castle, called Thrymheim, and began ruling over Jötunheimr from his castle. Meanwhile, the previous rulers of the land, Urðr and her two sisters, who no longer had the power they used to, were forced to retreat to the bottom of a certain frozen spring.

Thrym, not satisfied with just taking control of Jötunheimr, also began sending his minions to slaughter every one of Urðr's kin, the beasts roaming Jötunheimr. Doing so would render Urðr completely powerless and would allow his castle to float up to the plane above, Alfheim, thus allowing him to invade the land of the fairies and turn it to a land of frost, just like Jötunheimr. Thrym would then continue attacking the world of humans, Midgard, and then the home of the Æsir, Asgard, until he is able to reach the top of the World Tree to obtain the «Golden Apple», guarded by an impossibly strong eagle monster at the summit of the tree.

Irritated about being unable to easily destroy the Beast-type Evil Gods, Thrym and the frost giant generals invited the fairies to join them, supposedly offering Excalibur as a reward. However, as Excalibur is the only thing that is keeping the World Tree's blessings from restoring the land of Jötunheimr to its original state, Thrym would instead give the fairies the «Fake Sword Caliburn», a less powerful version of Excalibur, as a reward.

With this, Thrymheim's defenses became very thin, and Urðr used this opportunity to request help from the fairies to invade Thrymheim to put an end to Thrym's plot and restore Jötunheimr to its original state. However, as the real mastermind of this plot is another giant, named Þjazi, the only way to stop the castle of Thrymheim from breaking through the crust of Alfheim, is to remove Excalibur from its Plinth, before all of the remaining Beast-type Evil Gods are slaughtered.

Fairy Dance Arc
Kirito attempted to climb the World Tree twice to rescue the captive Asuna from Fairy King Oberon. The first time he attempted to beat the Guardian Knights and reach the top gate of the tree on his own, but was overwhelmed by the infinite number of knights and killed by them before he managed to reach the top. The second time, he attempted the quest with the help of Leafa and Recon as support; however that plan failed as the Guardian Knights had a different targeting algorithm than that of regular monsters, targeting support players as well as attacking players, thus making the division of roles in a party futile. During the battle, Recon sacrificed himself by using a self-destruct spell to destroy a large number of the knights, but even that wasn't enough. At that point, the Sylph and Cait Sith raid squadrons arrived and provided the firepower that evened out the odds, allowing Kirito to break through the wall of Guardian Knights and reach the top gate.



Once Kirito reached the gate, however, he found that there was no way to open it. Yui determined that the gate was never intended to be opened by players, as it was locked by administrator codes, thus preventing access to players even if they managed to reach the top. Kirito then remembered the admin card Asuna dropped from her cage and asked Yui to use the code from the card to unlock the gate. Yui was successful in unlocking the gate and the two were teleported to an area at the top of the World Tree. There, Kirito discovered that the rumored legendary city atop the World Tree did not exist.

Calibur
After Excalibur was removed from the Plinth of Thrymheim, the World Tree's roots began to regrow at an extraordinary speed until they sank into the restored Urðr's Spring. With the blessings of the World Tree restored, the flora of Jötunheimr regrew in mere moments and the barren wasteland returned to its once tranquil and flourishing state.

Trivia

 * After passing the Guardians in the first room of the Grand Quest, players were supposed to be able to use the door they were guarding to reach a so-called second room to fight against numerous large bosses, then a super giant boss in the third room, then a fourth room and so on.

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Árbol del Mundo Yggdrasil Иггдрасиль World Tree Arbre_du_Monde