One of the most dangerous biomes in this dimension, due to the dimension being deeper than the nether, some of the lava went through holes in the bedrock floor and got to the Stone Cold. this biome is filled with antimolten, basalt, and ash (antimolten is basically lava but cold, no it's not water), swimming in antimolten will have the same effect as falling into powdered snow but faster and has more damage. Ash is a powdery burnt substance originating from burning wood, it gives you an effect called "lung poisoning", lung poisoning deals half a heart and takes the ability to run away, the effect will last from 30 seconds to 2 minutes. although it may not seem worth the travel, in the biome is an ore called "Cryothite", more info in the Minecraftian ore section. Zombified piglins can spawn in this biome, the lore reason is that they accidentally fall into holes from the nether and fall into the Stone Cold.

Slicicle

A hostile mob that disguises itself as an icicle and waits until a player/mob comes by to kill it, they use their cryothite arms to slice or stab you, dealing the same damage as a diamond sword. they spawn in sculk remnants, ash canyons, and yeti domain, they're hostile towards pretty much anything that moves, except the warden (they run away from the warden if it's near). They can't be tamed at all and their lore is that they don't have any intellegence, their sole purpose is to kill and was given by the cryodra so it could kill all of the sculk in the dimension, but they ended up killing the cryodra because it wasn't specified for what they were meant to kill, which they killed the cryodra when they had the chance (the cryodra was starving).

Tankifiticus

a reptilian mob found in the ash canyons in the antimolten pools that is hostile and tamable with lava buckets (no you don't lose the bucket), it can attack by either biting, or opening its mouth and shooting out lava. When tamed, you can ride them, but you have to wear netherite or skulkium leggings, or you take damage like when you're standing on magma blocks.

Ash

Ash can only be found in the ash canyons, it may seem useless but it can be used to make the Potion of Polluting. Potion of Polluting if used, can give you the lung poisoning effect, useful if you're getting chased by endermen or mobs that can run.