Exploring the Abyssal Chasm Biome and Its Ocean Trench Structures
The Abyssal Chasm is one of the six cave biomes added by Alex's Caves, and exploring it means dealing with ocean trench structures, hostile deep-sea mobs, and a small set of building and food materials. The biome has a temperate climate, with a temperature value of 0.5, and it sits underground like the mod's other cave biomes. Because it is a rare destination rather than a common sight, preparation matters more than speed.
What Lives in the Abyssal Chasm
The Abyssal Chasm has a distinct split between what spawns on land and what swims in its waters.
- Monster spawns: deep one mage, deep one knight, deep one, spider, zombie, zombie villager
- Water creature spawns: squid, dolphin
The deep one family is the standout threat here. Three variants exist — the basic deep one, the deep one knight, and the deep one mage — and all three count as monster spawns alongside ordinary hostile mobs like spider, zombie, and zombie villager. The water creature list is much friendlier, limited to squid and dolphin.
Ocean Trench Structures
The Ocean Trench is a structure that generates inside the Abyssal Chasm biome, using the biome ID `alexscaves:abyssal_chasm`. Its placement follows a specific pattern: the game makes one attempt per 2x2 chunk region, and trenches must be at least 1 chunk apart from one another. That spacing makes the Ocean Trench a fairly frequent feature within the biome compared to other structures.
Abyssal Ruins
The Abyssal Ruins also generate in the Abyssal Chasm, using the same biome ID. Their placement is looser than the Ocean Trench: one attempt per 5x5 chunk region, with a minimum distance of 3 chunks between them. Abyssal Ruins also override mob spawning for the monster category, which means the structure takes over hostile spawns in its area rather than sharing them with the biome's normal monster list.
Deep-Sea Materials
The Abyssal Chasm's material set is built around 
Abyssmarine and its processed forms. Both crafting and stonecutting can produce the higher-tier blocks, so you have options depending on what stations you have available.
- Crafting (shaped): Abyssmarine x4 →
Abyssmarine Bricks - Stonecutting: Abyssmarine → Abyssmarine Bricks
- Crafting (shaped): Abyssmarine Bricks x4 →
Abyssmarine Tiles - Stonecutting: Abyssmarine Bricks → Abyssmarine Tiles
- Stonecutting: Abyssmarine → Abyssmarine Tiles
Note that tiles can be reached two ways through stonecutting — either from bricks or directly from Abyssmarine — while the crafting route always passes through bricks first.
Deep Sea Sushi Roll
The 
Deep Sea Sushi Roll is a food item made with a shapeless recipe. The ingredients are 
Tripodfish, 
Sea Pig, 
Lanternfish, and 
Dried Kelp. Because the recipe is shapeless, the arrangement of the ingredients in the crafting grid does not matter — only that all four are present.
Practical Notes
Bring gear suited to both hostile mobs and underwater travel, since the biome mixes deep one variants and undead with squid and dolphin in its waters. If you are hunting for structures, remember the spacing rules: Ocean Trenches appear roughly once per 2x2 chunk region with a 1-chunk minimum gap, while Abyssal Ruins are rarer, at one attempt per 5x5 chunk region with a 3-chunk minimum gap. Collect Abyssmarine while you explore, since it feeds every recipe in the material chain, and gather the four fish and kelp ingredients if you want to craft a Deep Sea Sushi Roll.
Covers the mod’s in-game guide topics: Abyssal Chasm Ocean Trench Abyssal Ruins Abyssmarine Bricks Abyssmarine Tiles Deep Sea Sushi Roll