Jötunheimr

Jötunheimr (ヨツンヘイム) is the most difficult field of «ALfheim Online». Located underground beneath its environment is dark and frigid, and its floor is infested with evil-god class monsters. High above the ground in the center of the ceiling hangs an inverted ice pyramid containing the «Holy Sword Excaliber». There are several ways to get to Jotunheim. Besides the entrances at the end of the dungeons located North, South, East, and West of the city of Aarun, and the path through the digestive tract of a giant worm mimicking a village on the Arun Plateau; there is also a secret doorway in Aarun that leads directly to Jotunheim below, but one requires a way to get down to the surface.

There are two types of evil-god class monsters, one is «Humanoid Type» the other is «Beast Type». The humanoid types are controlled by King Priam, the beast class is under the protection of the three fates of Norse mythology, Verdande, Urd, and Skuld. According to Urd, Jotunheim was once like «Alfheim», with the blessings from the world tree Yggdrasil, covered in the beautiful water and greenery. Urd and her tribe, the Rock Giant Tribe, lived in harmony with the «Beast Type» monsters currently in this dungeon. After stealing Excaliber, King Priam threw the sword to Urd's Spring which is the center of Jotunheim  The sword severed the thick roots of the world tree, and in that instant, Jotunheim no longer received the blessings from Yggdrasil. Where there was once a great lake now is known as the «Great Void», and directly above the void is the inverted pyramid made of ice which was once part of the lake that is now frozen, and inside the pyramid lies the «Holy Sword Excaliber».

Fairy Dance Arc
After Kirito and Leafa are seemingly "eaten" by a giant worm-class monster, they realized they have fallen to the land of Jötunheimr deep below Alfheim and the World Tree. After assessing their situation, Kirito and Leafa decide to find a way back to the surface world. They then come to notice two evil-God-class monsters fighting each other, which confused them at first due to the fact that NPC monsters should not be able to fight among each other. As they watched the gigantic battle, they witnessed a «Humanoid-type» and a «Beast-type» evil-god-class monster fighting, with the former gaining the upper hand. Feeling pity, Leafa wanted to help the «Beast-type» monster, which looked like jellyfish with an elephant's head, from being bullied by the «Humanoid-type», which surprises Kirito. After gaining the attention of the «Humanoid-type» monster, Kirito and Leafa lead it a nearby frozen lake with Yui's direction. After approaching the frozen lake, due to its massive size and weight, the «Humanoid-type» monster broke the ice layer of the lake and nearly drowned and kept approaching Kirito and Leafa. With the «Beast-type» monster recovered, it dived into the lake and finished off the «Humanoid-type» monster.

After the tiring event, Kirito and Leafa asked each other on the next course of action, when suddenly the «Beast-type» monster reappeared before them but not out of hostility. Yui suggested that this "child" did not mean any harm to them. After realizing that it wanted to carry them on its shoulders, the «Beast-type» monster gently picked them up with its long nose and place them on it back. Swimming around the lake. Upon approaching a big void, the «Beast-type» monster seemed to stopped and did not move. Surmising that might be the end of its journey, Kirito and Leafa decided to find the exit to the upper world, only to be suddenly interrupted by a group of Undine players that were hunting in the dungeon. After being forced aside so the group could kill the evil-god-class monster, Leafa again took pity on the creature, having helped them in their journey to find a way out of Jotunheim  Kirito then affirmed Leafa's feelings and decided to help the monster by attacking the hunting group. One by one, first targeting the mages on the back row, Kirito and Leafa managed to defeat 5 players before being overwhelmed by the hunting party until suddenly the «Beast-type» monster let out a huge shout and it began to light up. Soon the water-based «Beast-type» monster sprouted wings and let out a high-class magic, Dispel Field. After overwhelming the hunting group it returned to where Kirito and Leafa were and offered another ride, this time flying around Jotunheim Its flight path circled them around an inverted pyramid hanging at the top ceiling of the Jotunheim just below the World Tree roots. Kirito and Leafa then noticed a shining object, after seeing it, Leafa confirmed that it is the Legendary weapon know as «Holy Sword Excaliber». But since they figured that it would be impossible for the two of them to obtain it, they decided to keep this location a secret and  to come back for it another time. After leading them to spiral staircase, they bid farewell to their new firiend «Tonkii» and proceeded up the staircase to Aarun City.

Caliber
Players were given a quest to retrieve Excaliber by defeating the «Beast Type» evil-god class monsters. This quest was soon revealed to be a fake and if it were completed would lead to the invasion of the upper world of «Alfheim» by the «Frost Giant Tribe» or also known as the «Humanoid Type» evil-god class monsters. The real quest to obtain Excaliber required players to talk to the NPC Urðr and accept her quest to venture into the inverted pyramid housing the sword and remove it. Before removing the sword, players need to battle King Þhrym as a boss.

After completing the quest, the party receives Excaliber and restore Jötunheimr to its former glory.

Trivia

 * Supposedly, in Norse mythology, "Jötunheimr is one of the nine worlds, which is the home of giants". Jötunheimr is also sporting a castle in which Loki resides.
 * It is also a mountain range in Norway (Jotunheimen).
 * In Icelandic, it translates as "resounds".