The Dirt Biome, with The Core at its centre, is the starting area and is always at the centre of a world. It effectively extends into the neutral border zones between the progressively more challenging biomes. Biome angular positions, and order of the outer biomes, are randomised on creation of a new world.
The inner biomes are obvious finite. But the three outer biomes are theoretically unlimited in size, with dynamic world generation creating more chunks as players move.
The Great Wall is an unbreakable wavy structure that initially surrounds the three inner biomes. The Wall occupies the gap from 450 to 520 tiles and gates access to the outer biomes, in Game Progression.
Dirt biome is where your character starts at. The walls of this area are so soft that you can mine them without any tools, but using pickaxe break those walls more easily.
Slimes are common but they are not aggressive unless attacked first. Red slimes, however, should be approached with caution as they will attack anyone who get close.
Mines: Copper Ore
The clay caves is the biome next to dirt biome. Miners will require resources from the clay caves to craft various tools and equipment to mine the forgotten ruins.
You will still encounter slimes here, with the addition of larvae. They are small, but plenty, making them dangerous in pack.
Larva hive biome is a sub-biome of the clay caves. The walls and grounds are covered with larva hives that makes them as tougher than stones. Slimes no longer spawn here, but larvae are much more common. You may find traps and acid on the ground, which can be removed for safe exploration. The Larva hive biome is also where the The Hive Mother boss is found.
The forgotten ruins, like the clay caves, lies next to the dirt biome. Due to the random nature of the underground, many miners find themselves in the forgotten ruins before the clay caves. When that happens, simply go back to the core, and mine towards the opposite direction.
This place is the natural habitat of various cavelings, who will defend their home against any unwelcome guests.
Azeos' Wilderness is a lush and vibrant forest. This biome is one of the brighter areas of the underground. You may find various plantation and animal farms, as caveling gardeners have made it their home here. Be wary of caveling hunters, as they can disguise themselves to catch any unsuspecting miners.
Mines: Scarlet Ore
Mold biome is a sub-biome of the Azeos' Wilderness. This area has been infested with fungi, with mold growing everywhere you can touch. The caveling residents here have been infected by fungi parasites, making them more aggressive but mindless.
A dungeon sub-biome found within the The Sunken Sea. It has a run down hi-tech theme and features various scenes representing other parts of the world, with many decorative items to loot. Caveling Scholars are in residence, supporting the occasional Core Sentry.
The third and final infinite outer biome. Its open expanses of Desert Sand Ground are a battleground between the explosive Bomb Scarabs and formidable Caveling Assassins.
Large areas of Sandstone Wall divide up the desert, concealing sources of colorful Galaxite and other surprises.
Dotted throughout are a large number of oasis, temple ruins and intact temple dungeons with loot. Various unique scenes includes the Titan Temple and its associated mazes. Molten Quarry sub-biomes also found here.
Mines: Galaxite Ore
Molten Quarry is a volcanic sub-biome of The Desert of Beginnings. It's blackened terrain is riven with lava and burning hot Ground Magma Slime, which spawns fiery foes.
The lava itself overrides the desert biome with it's own fishing loot tables. The native fish give powerful, unique cooked food buffs. Particularly the legendary Starlight Nautilus.
Igneous and the Ancient Forge are both found here. Both essential for crafting the Soul Seeker Pickaxe.