The Arctic Abyss is the rarest biome added by NetherEx. It is cold themed biome in the Nether with Icy Netherrack covered in Frostburn Ice and lava lakes cooled enough to turn into magma. You will also not find any lava pockets in this biome. Just like all biomes in NetherExNether Quartz and Glowstone can be found here. It is also the only place to find Nether Rime Ore and pools of Ichor. A variety of new mobs will naturally generate here, including the Frost, Coolmar Spider, Wight, and Brute.