|Spoiler Alert: This article or section contains details about plotlines not covered in the anime. Do not proceed unless you wish to be spoiled. |
The 27th Floor (第27層, Dai 27-sō?) of Aincrad is a floor of perpetual darkness, with very few openings in the exterior of the floor, meaning that no sunlight shines in the floor even during the day. The floor is rich in ore items, therefore, the floor was popular among the artisan players in Sword Art Online.
The floor is filled with craggy, rocky mountains and, in terms of impression, the floor is quite similar to the underground of the Gnome territory in the north of Alfheim—numerous stalactites hang unevenly from the ceiling of the next floor and, above those, are large prismatic gems which let out a hazy blue glow.
Settlements and Notable LocationsEdit
Ronbaru is a night elf-theme city, located at the bottom of a wide circular valley of the floor. The town is carved out of one of the rocky mountains that are abundant on the floor.
The Labyrinth, like Ronbaru, is also carved out of one of the mountains that are abundant on the floor. Many crystal hexagonal prisms about the size of small houses stretch out from the base of the tower, hazily illuminating the tower with a blue phosphorescence. Shortly after the entrance, the natural cave gives way to a slate-tiled, man-made tunnel.
On June 22, 2023, members of the Moonlit Black Cats came to the Labyrinth of this floor to hunt for Cor to arrange a function when their guild leader, Keita, came back with the keys to their new guild home. However, after they earned the targeted amount of money, Ducker found a hidden room with a treasure chest. Due to the insufficient level of his trap dismantling skill, he triggered a trap that lead to continuously spawning Mineral Elementals and Dark Dwarf Miners, while an Anti-Crystal Area prevented the use of Teleport Crystals. Kirito was the only member of the guild present in the battle who managed to survive and was burdened with the guilt of the death of his guildmates ever since.
The 27th Floor in New ALfheim Online was reached between December 24, 2025 and January 6, 2026, while the boss room was discovered by January 8, 2026. The Sleeping Knights challenged the boss on January 8, 2026, but they were wiped out as the boss revealed its last resort attacks. As another guild had used «Peeping» to spy on their battle, by the time the Sleeping Knights returned to the Boss Room, 20 players had already blocked off access to the room. After Kirito arrived and stalled the main force of the guild, the Sleeping Knights broke into the Boss Room and sealed themselves in. After 40 minutes of intense battle, Asuna realized what the weakness of the boss was and had Yuuki finish off the boss by using her Mother's Rosario Original Sword Skill to deal 11 hits at its weak point.
- Metallic elemental-type boss (SAO version Labyrinth Boss) 
- The Four-Armed Giant (ALO version Labyrinth Boss)
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