The enclosed world where the Norns wake: warm, humid, strangely orderly, and layered from a lit canopy down to hot mineral dark. Everything in it is close at hand, and not everything about it is explained.
The Interior is divided into six distinct biomes distributed across four vertical layers. Five run through the inhabited layers; the sixth lies on the far coast — the steaming Ashen Tidepools.
The topmost inhabited layer of the Interior, and the first place the Norns wake. The Fungal Grotto is defined by enormous bioluminescent fungi whose spore-light illuminates a canopy of living material. Moisture is constant. The air carries a faint sweetness, like the world breathing.
The Grotto is the most welcoming region for new life — food is abundant, predators are minimal, and a mycelial network runs beneath the substrate, carrying chemical signals the Norns can sense but not read. Not yet.
Primary inhabitants: Norns
A wide horizontal plateau running the circumference of the Interior, thick with conventional plant life, running water, and the most complex surface ecology of any region. The Shelf is where the world is most alive — and where the consequences of life are most visible. Seasons exist here in ways they don't in the controlled environment of the Grotto above.
Primary inhabitants: Norns
Deep below the Verdant Shelf, the substrate crystallizes. The Crystal Caves are a vast network of mineral formations whose resonant properties make them unlike anything above. The caves grow. The crystals add new facets. Nothing about them ever seems finished.
Among the formations, the Norns find old seals and runes — regular, patient marks that no one living seems to have made. They are easy to walk past, and hard to forget once noticed.
Primary inhabitants: Norns
The Threshold is less a place than a condition: the boundary zone between inhabited layers. It exists wherever the world changes register — where Grotto gives way to Shelf, where Shelf meets Crystal Caves, where the Caves open onto the Deeps. To stand in the Threshold is to stand in a transition, and the Norns tend to pass through it quickly.
Primary inhabitants: Norns
Below the Crystal Caves, the world becomes inhospitable to most life. The Deeps are hot, mineral-dense, and lit only by geological events. The Grendels make their home here — their adrenaline chemistry, their territorial instincts, their resistance to toxins that would kill any surface creature, are all adaptations to an environment that has been trying to kill them since before they had names for what they were.
Primary inhabitants: Grendels
The sixth biome: dark skies over ash-toned ground at the world's far coast. It is its own region, distinct from the layers above, and few Norns ever see it.
The Interior is structured vertically as much as horizontally. Resources, danger, and cognitive challenge all scale with depth. The Norns begin at the surface and discover the world layer by layer, as complexity earns itself.
The Fungal Grotto and the upper Verdant Shelf. Most accessible. Highest food abundance, lowest ambient danger. The starting world for Norns. Challenges here are complex enough to drive growth, dangerous enough to require cooperation, and safe enough to allow recovery from mistakes.
The deeper Verdant Shelf and the Threshold's upper reaches. The world becomes more complex here: ecosystems more interdependent, resources requiring more sophisticated extraction, and competition for them growing sharper.
The Crystal Caves, the lower Threshold, and the upper Deeps. Darkness requires adaptation or technology. The old seals and runes are most concentrated at this depth.
The deepest layer, inhospitable to most surface life. The Grendels live here. Most Norns will never reach the Deeps. The ones who do are not the same afterward.