The Dragons' Den (竜の巣, Ryū no Su?, lit. "Nest of Dragons") is a bonus dungeon in Final Fantasy VI Advance located just north of the Dragon's Neck Colosseum on an island with a single tree. Access is given once the player has defeated the Eight Dragons. In the dungeon lie the most powerful equipment pieces in the game, but also the most powerful bosses guarding them.
The den requires three parties to traverse, which lets the player exploit the Save Point Glitch. There exist several save areas with red beams of light that allow the player to change party members between the three parties if all three are brought to the same room. This means the three parties can often change paths and meet up with the other two. Ultimately, this means the player can explore the den with the same party and fight all eight dragons with them, if they know the den well enough and are willing to backtrack.
Several areas of the den are sealed off with magical barriers attuned to one of the eight dragons. Defeating a dragon shatters all corresponding seals, allowing the player deeper access into the den. To access the den's deepest areas, all dragons must fall. Each dragon is stronger than before with higher stats, better attacks, and each has some sort of unique special "gimmick" to make the fight difficult; Ice Dragon mimics the Vector Lythos and attacks in a group of four, while Gold Dragon gains a Runic effect, absorbing all magic cast against it.
The dungeon architecture changes several times, and various puzzles from previous dungeons, such as jumping on turtles to cross water or hopping over bridges, are repeated. The dungeon is mostly a series of caves, some with magma, but a temple area also appears. In the deepest area of the dungeon lay three switches. Upon two of the switches being triggered, the third becomes a portal to the room where Kaiser Dragon lurks. After Kaiser is defeated, returning to his chamber reveals Omega Weapon in his place.
The monsters of the Dragons' Den are powerful, and should not be underestimated. A wide variety of monsters is found in the Dragons' Den, and no single monster is found in every section of the lair; some can only be found in very specific rooms. Most of the enemies are unique to the Dragons' Den, though there are a number of enemies from Kefka's Tower and other locations. Excluding a handful of monster-in-a-box enemies and the dragons themselves, all of the monsters which are unique to the Dragons' Den give 5,000 experience upon defeat.