Astral Mountains Cavern

Who spawns

Common

LunarisLv 38–4215.4%MaraithLv 38–4215.4%TombatLv 38–4215.4%SibelyxLv 38–4215.4%Reptyro CrystLv 42–4415.4%

In water

WhalaskaLv 42–4450%PolapupLv 42–4450%

Bosses

PengulletLv 39–455%Mau CrystLv 39–455%ChilletLv 39–455%SibelyxLv 42–455%CryolinxLv 42–455%Vanwyrm CrystLv 42–455%ElphidranLv 42–455%WumpoLv 42–455%Mammorest CrystLv 42–455%ReindrixLv 42–455%QuivernLv 42–455%Reptyro CrystLv 42–455%Suzaku AquaLv 42–455%MaraithLv 39–455%LunarisLv 42–455%TombatLv 42–455%PolapupLv 39–455%MunchillLv 39–455%IcelynLv 39–455%FrostplumeLv 39–455%

Chest loot

Ordinary chest

Gold Coin×2000–2500100%High Quality Bait×2–3100%Large Pal Soul37.8%Reinforced Arrow×5–1026%Giga Sphere×1–326%Reindrix Stew×1–226%Hyper Sphere18.9%Training Manual (L)×2–317%Gold Key15.1%Training Manual (XL)×1–25%Medical Supplies3.8%Recovery Meds2.3%Semi-Auto Rifle Schematic 12.3%Semi-Auto Shotgun Schematic 12.3%Metal Bat Schematic 12.3%Katana Schematic 12.3%Assault Rifle Schematic 12.3%Pump-Action Shotgun Schematic 12.3%Refined Metal Armor Schematic 11.5%Refined Metal Helm Schematic 11.1%Heat Resistant Refined Metal Armor Schematic 10.8%Cold Resistant Refined Metal Armor Schematic 10.8%Semi-Auto Rifle Schematic 20.5%Semi-Auto Shotgun Schematic 20.5%Metal Bat Schematic 20.5%Katana Schematic 20.5%Assault Rifle Schematic 20.5%Pump-Action Shotgun Schematic 20.5%Refined Metal Armor Schematic 20.3%Refined Metal Helm Schematic 20.2%Heat Resistant Refined Metal Armor Schematic 20.2%Cold Resistant Refined Metal Armor Schematic 20.2%Semi-Auto Rifle Schematic 30.1%Semi-Auto Shotgun Schematic 30.1%Metal Bat Schematic 30.1%Katana Schematic 30.1%Assault Rifle Schematic 30.1%Pump-Action Shotgun Schematic 30.1%Refined Metal Armor Schematic 30.1%Semi-Auto Rifle Schematic 40%Semi-Auto Shotgun Schematic 40%Metal Bat Schematic 40%Katana Schematic 40%Assault Rifle Schematic 40%Pump-Action Shotgun Schematic 40%Refined Metal Helm Schematic 30%Refined Metal Helm Schematic 40%Refined Metal Armor Schematic 40%Heat Resistant Refined Metal Armor Schematic 30%Heat Resistant Refined Metal Armor Schematic 40%Cold Resistant Refined Metal Armor Schematic 30%Cold Resistant Refined Metal Armor Schematic 40%

Special chest

Gold Coin×2800–3100100%Innovative Technical Manual32.3%Ancient Technical Manual×1–232.3%Bellanoir Libero's Slab25.3%Treasure Map No. 310.1%

Dungeons of a biome are scattered across that region, but the game data has no 'this cave = this dungeon' map link — the entrance is assigned procedurally.