The Deep Dungeon is a very mysterious and dangerous place to be. Only the strongest warriors and magicians will want to travel here.
The Deep Dungeon can be accessed in Chapter 4 by going to the bar at Warjilis Trade City and reading the rumor. A path will appear and take you to an island.
This place is dark. Very dark. What do I mean by that? I mean that you can't see the ground beneath your feet because it's pitch black. There are also 10 levels to this place, each consisting of its own hidden door in the ground to take you down a level. You can only find the door by searching. You have to take your characters across the landscape, square by square, and one of them will eventually tell you that they've found the door. I would gladly tell you where the doors are, but the game randomly selects a spot on the landscape each time you enter.
There is a way to light up the room. Once you've defeated an enemy, they may leave a crystal and that will light up the room a little. Four enemy crystals will light the cavern up completely.
Here are the names of the seperate levels:
NOGIAS
TERMINATE
DELTA
VALKYRIES
MLAPAN
TIGER
BRIDGE
VOYAGE
HORROR
END
You must fight Serpentarius... a pretty easy boss at this point in the game if you have enough levels. This boss is the only way you can learn the Zodiac Summon Spell. You can learn the spell by getting hit by the spell as a Summoner... and surviving. This means you'll have to use shell on your summoner and knock down the Magic Attack Points off of the boss. Also, after defeating the boss, you'll recieve a 13th Zodiac Stone called Serpentarius (go fig).