Lodestone Cavern

The Lodestone Cavern, also known as the Magnetic Cave, the Magnetic Cavern, Cave Magnes, or the Cave of Power, is a cave in Final Fantasy IV, located on a small, densely forested island to the northeast of Troia. The cave is home to the Dark Elf, who stole the Crystal of Earth from Troia. The Dark Elf perpetuates a strong magnetic field in the cave that leads to anyone wearing metal equipment to be rendered helplessly paralyzed in battle.

Final Fantasy IV
Cecil Harvey, Tellah, Yang, and Cid Pollendina arrive to the Lodestone Cavern in order to retrieve the stolen Earth Crystal. At the bottom floor, they confront the Dark Elf, but are defeated by it. Using the Whisperweed, Edward plays a tune that is transmitted to the heroes' corresponding Whisperweed which dispels the magnetic field, allowing Cecil and his friends to defeat the Dark Elf and recover the Earth Crystal.

Final Fantasy IV: The After Years
Palom and Leonora head into the cavern to evade Baron's soldiers while fleeing with the Earth Crystal, hoping that the metallic field will slow them down.

The soldiers strip themselves of their weapons and armor, chasing the two mages into the Crystal Chamber. There, the Dark Elf (The After Years) is accidentally awakened by Leonora. They are powerless against its dragon form, until Maenad summons Shiva to destroy it. They attempt to trick Maenad, but she uses Shiva to defeat the heroes as well.

The Crystal is stolen, and the heroes are left near-dead on the floor.

Treasure

 * 500 accumulated GP
 * Potion x2
 * Mega-Potion
 * Ether x2
 * Hi-Ether
 * Remedy
 * Phoenix Down
 * Fairy Claw

Final Fantasy IV

 * Cait Sith, Needlehog x3
 * Ogre x3
 * Cave Bat x3
 * Ogre x2, Cait Sith x2
 * Succubus, Cave Bat x3
 * Succubus, Cave Bat x6
 * Mind Flayer x2
 * Cave Naga, Twin Snake x2
 * Dark Elf (boss)
 * Dark Dragon (boss)

B1F

 * Cave Naga, ラメイジ
 * ラメイジ, Ettin Snake x2
 * Cave Bat x3
 * Ettin Snake, Needlehog x2
 * Cait Sith x2
 * Mindflayer x2

B2F

 * Ettin Snake, Needlehog x2
 * Ettin Snake, ウィルプリースト, ラメイジ
 * Succubus, Cave Bat x3
 * Mindflayer x2
 * Cave Naga, ラメイジ
 * ラメイジ, Ettin Snake x2
 * Cait Sith, Cave Naga
 * Cait Sith x2

B2F (Small Room)

 * Mindflayer x2
 * Mindflayer, Cait Sith, Cave Naga
 * Ettin Snake, ウィルプリースト, ラメイジ
 * ラメイジ, Ettin Snake x2
 * Cave Naga, Ettin Snake x2
 * Cait Sith x2
 * Flood Worm, Cait Sith, ラメイジ
 * Succubus, Cave Bat x3

B3F

 * Mindflayer, Cait Sith, Cave Naga
 * Succubus, Cave Bat x3
 * Cait Sith x2
 * Mindflayer x2
 * Cait Sith, Cave Naga
 * Needlehog x2, リカルトメイジ, ラメイジ
 * Flood Worm, Cait Sith, ラメイジ
 * ラメイジ x2, リカルトメイジ

B3F (Small Room)

 * Ettin Snake, ウィルプリースト, ラメイジ
 * Succubus, Cave Bat x3
 * Flood Worm, Cait Sith, ラメイジ
 * Needlehog x2, リカルトメイジ, ラメイジ
 * Cave Naga x2, Ettin Snake x2
 * Cait Sith, Needlehog x3
 * Flood Worm, Cait Sith x2
 * ウィルプリースト, Ettin Snake, Hydra

B3F (Passage)

 * Cave Naga x2, Ettin Snake x2
 * Succubus, Cave Bat x3
 * Cait Sith, Needlehog x3
 * Needlehog x2, リカルトメイジ, ラメイジ
 * Mindflayer, Cait Sith, Cave Naga
 * ウィルプリースト, Ettin Snake, Hydra
 * Flood Worm, Cait Sith, ラメイジ

B4F

 * Cave Naga x2, Ettin Snake x2
 * ウィルプリースト, Mindflayer, Cave Naga
 * Succubus, Cave Bat x3
 * ラメイジ x2, リカルトメイジ
 * ウィルプリースト, Ettin Snake, Hydra
 * Flood Worm, Cait Sith, ラメイジ
 * Mindflayerx1, Cait Sith, Cave Naga

B5F

 * Cave Naga x2, Ettin Snake x2
 * Needlehog x2, リカルトメイジ, ラメイジ
 * ウィルプリースト, Mindflayer, Cave Naga
 * ウィルプリースト, Ettin Snake, Hydra
 * Cait Sith x2, Needlehog x2
 * Cait Sith x2, リカルトメイジ, Cave Naga
 * Flood Worm, Cait Sith, ラメイジ
 * Mindflayer, Cait Sith, Cave Naga

Music
The background theme that plays inside the Lodestone Cavern is Final Fantasy IV's "Dungeon" theme.