After you've collected all the treasures inside Damcyan Castle, use hovercraft toward east you'll see another cave. This is the Antlion's den where you'll collect the following items:
- Spider Silk (x2)
- Potion (x4)
- Tent
- Gold Needle
- Lamia Harp
- Phoenix Down
- Emergency Exit
- Ether
- Shadowblade
- Ice Rod
Boss: Antlion
Strategy: use physical attacks when it's eyes turn red and use magical attacks when it's eyes turn back to white. After the battle, use Emergency Exit to exit or you can walk back.