Before its appearance, the town was in an economic crisis, having no visitors from outside and very little appeal to it that could give the town actual profit. However, with the labyrinth's sudden appearance, the town is becoming alive again due the large amount of explorers coming, giving large profit to the town and its establishments such as the inn, shop and hospital. The Explorers Guild was also established to help adventurers organize and form guilds.
Emerald Grove is the first stratum and the entrance to the forest. It is a lively woods, full of lush and a very pleasant atmosphere. Its lower reaches are guarded by a wolf pack, led by the fearsome Fenrir.
Primitive Jungle is the second stratum. It is a green, humid jungle, home of powerful creatures. This is a much less friendly environment than the previous one, where even plants have extremely effective killing methods. Before leaving this wild maze, one must defeat the king of the jungle, Cernunos.
Azure Rainforest is the third stratum, and the first one no one has reached ever since the exploration of the labyrinth began. It is a cool, wet forest, almost appearing as if it is underwater. It is home to many species of creatures, with an ant nest on B12F. There have even been sightings of a strange, humanoid creature on those lands. If one has the resolve to brave this difficult environment, they will have to face two very powerful enemies: Royalant, the queen of the ants and Cotrangl, the master of both water and air elements.
After getting through forests full of life, the Sandy Barrens may surprise some. This desert is home of the Forest Folk and some of the labyrinth strongest beasts. The Forest Folk are unwilling to let you reach the deepest reaches of the labyrinth and must be defeated in order to advance. On B20F, to reach the labyrinth's last stratum, you must defeat their main army led by Iwaopeln, their guardian beast. With their defeat, the road to the last stratum is open, and the labyrinth's final secret will be revealed.
Lost Shinjuku is home to the biggest secret of the labyrinth. This giant city of the past is completely destroyed and contains technology far more advanced than that of the present day. The area explored is formed by two buildings that are linked by bridges. As you explore the city, you find notes that tell more about its history and the reason behind its destruction. During your exploration, you will meet two well know faces who will try to stop your advance. In the final room, you will meet the mastermind behind the events that took place in the labyrinth, and will face it in a final confrontation for survival. You might think this is finally the end, and that all of the labyrinth's secrets have been revealed. However, if you come back to the final room after the credits, you will find an entrance leading to the core of Yggdrasil...
This Stratum is the ruins of the Shinjuku district of Tokyo, and possibly what's left of Japan itself.
Claret Hollows is the the core of the labyrinth and the final stratum. This disturbing cave, with walls made of flesh and skeletons around the floor, is home to the strongest monsters of the labyrinth, and has some extreme ways to keep explorers away from the core. If you have the courage and the strength, you will eventually reach the deepest floor, and face the most powerful enemy in the labyrinth: Primevil, incarnation of the Yggdrasil core.
- This is an optional post-game stratum, for those who wish to test their skills. This stratum is not to be taken lightly, and has broken even the most hardcore adventurers.
- There are some interesting (although unconfirmed) theories of the symbology behind the strata order. Etrian Odyssey I's labyrinth is theorized to be shaped after the stages the world went after the apocalypse. First, Lost Shinjuku symbolizes the world right after the apocalypse. After that, it went through a desert stage, symbolized by the Sandy Barrens, where life was nearly impossible. Ages have passed, and, slowly, life started returning to normal. The environment eventually became very humid. Lifeforms started to evolve, leaving the water, and began to live on land again. The Azure Rainforest is shaped after this stage. With more evolved life forms, the world changed again, into a less humid climate, where different and stronger kinds of animals and plants developed themselves in order to survive in the harsher environment. This stage is symbolized by the Primitive Jungle. Finally, with stronger and more adapted life forms, it took its final and current form, as a fair weather green world, full of life, which is the Emerald Grove.
- Another, darker theory, is that Etrian Odyssey I labyrinth symbolizes the descend to hell, starting on a fair world, full of life, and each time you descend a stratum, changing into a harsher, harder to survive environment. In the end, the explorers find themselves on a claustrophobic cave with walls made of flesh, skeletons around the floor, and nightmarishly powerful creatures living on it.