Only the most powerful Aislings can enter Kasmanium
Mine. The creatures and treasures deep inside are the stuff of legends.
Kasmanium Mine (minimum insight - 86, 99 for second level)

Common Monsters:
Draco, Orc, Goblin, Grimlock

Common Spoils:
Ard Ioc Deum, Lapis Ring, Grave Ring

Other Features:
Other than the above items, and monster skulls, Draco's Jaw, etc. rare metals can be found in Kasmanium Mine.