With the Unicorn's Horn in hand, your next destination is the Cave of Spirits, located south of Euclid. This cave is a dark and winding dungeon, home to earth-elemental monsters. You'll encounter enemies like Goblins, Trolls, and Earth Elementals. The cave features several branching paths, some leading to dead ends or treasure, while others progress the story. It's advisable to bring plenty of Torch items or use Mint's 'Illuminate' spell if available, as visibility can be poor in some sections.
Your primary objective is to find the Earth Spirit, Gnome. You'll need to navigate through the cave's puzzles, which often involve pushing boulders or activating switches. Eventually, you'll reach Gnome's chamber. After a dialogue sequence, you'll be forced to battle Gnome to prove your worth. This is a significant boss fight, so ensure your party is well-equipped and healed. Defeating Gnome will grant you his power, a crucial step in your quest to defeat Dhaos. After the battle, Gnome will join you as a summon, and you'll be able to exit the cave.