Spectrum's New Biomes, Dimensions, and Structures
The Deep Barrens
The Deep Barrens is a dark, stony wasteland found far below the surface. At first glance, it appears empty, but this biome rewards careful exploration. Ores are visible from nearly every angle, embedded in the rock around you. The most striking feature is the presence of gigantic ore veins that crisscross the terrain. A single one of these veins can provide enough material to last for a very long time, making this a high-value destination despite its grim appearance.
Deep Dripstone Caves
These caves feel familiar to those who have explored standard dripstone caverns, but they are distinctly different. The scale is the first thing you will notice. The dripstones here are enormous, suggesting these formations have been growing since the earliest ages of the world. You may encounter giant stalactites that span hundreds of blocks in length. The floor is not dry; it is dotted with numerous puddles of water, which adds a reflective sheen to the cavern floor and creates a damp, ancient atmosphere.
The Abyssal Depths and a New Dimension
Beyond the familiar caves lies a place that defies expectation. As you dig deeper and break through the bedrock layer, you can discover a pitch-black portal. This portal is the gateway to a new dimension, a realm that has never seen sunlight. It is a place of eternal darkness, where no light has reached for eons. The description of this place suggests a haunting, unknown environment. The biomes found within this new dimension, referred to as Abyssal Biomes, are a subject of curiosity. Without sunlight, the typical requirements for life are absent, yet the area is described as diverse. What forms of life or vegetation could exist in such conditions remains to be seen, but the implication is that the reality of this place contradicts expectations.
Generated Structures: Undergrowth Manor
The Undergrowth Manor is a structure that generates in specific locations. It has a placement rule of one attempt per 60x60 chunk region, with a minimum distance of 40 chunks between any two manors. This structure has a significant effect on its surroundings: it overrides the normal spawning of many mob categories. This includes ambient creatures, axolotls, general creatures, misc mobs, monsters, underground water creatures, water ambient mobs, and water creatures. This means that within the structure's area, the standard rules for what spawns are replaced by the structure's own specific rules.
Generated Structures: City Below
The City Below is another major structure, found in a different set of locations. Its placement is more frequent than the Undergrowth Manor, with one attempt per 24x24 chunk region and a minimum separation of 16 chunks. Like the manor, the City Below also overrides mob spawning for the same broad set of categories: ambient, axolotls, creature, misc, monster, underground water creature, water ambient, and water creature. This override suggests that both structures are not just static ruins but are active, controlled environments with their own unique ecological or hostile conditions. When you find either structure, be prepared for a change in the usual rules of engagement.
Covers the mod’s in-game guide topics: Abyssal Biomes Deep Barrens Deep Dripstone Caves Delving Deeper Down Undergrowth Manor City Below