Once we have gotten a few jobs from the Fire Crystal, adjust your gear and item set as you want to back in the Dwarven Hollows. Remember to buy the Diamond Bell if you opted for a Geomancer.
Speak with the guard as before to give him the Horns of Ice and receive a Magic Key. You'll also be given access to a large treasure trove! Use the southeast passage to reach it.
So, stuff to mention about them. The Ottershroom makes you high. ... just kidding, it is an out-of-battle Teleport. The Gauntlets are arm gear for Knights and Warriors. The Scholar Robe and Hat are good for, obviously, Scholars. Knight Armor is the best thus far and only for Knights. The Books are weapons for Scholars; choose an element you prefer. Medusa Arrows are used by Rangers and may even Petrify, and the Heroic Shield for Knights/Warriors is very useful, as it raises a fair number of stats, and guards from a lot of statuses.
Now, let's leave. As you do, you'll meet up with an injured person. After the scene, let's head to the overworld.