Red doors are everywhere in , but you need to find a special item called the Thief's Key to open them. Those with the key to every red door can unlock various treasures, including rare gear and plenty of Gold.
This elusive tool should be one of the first things your party tracks down when you start your adventure. The Thief's Key is not just an exploration item, as it is also needed to progress the changed story of .
When you arrive in the town of Reeve, you will be tasked with tracking down this item, but not given many clues about where it might be.
By talking to the right people, you can gain some clues that will help you discover the Thief's Key's location. Do not mistake the Thief's Key with the Magic Key, as the first opens red doors around the world while the latter opens blue doors locked in many different locations.
The first step to finding the Thief's Key starts when you go to the jail within Aliahan Castle. You can find this area in the southeast of the larger Castle, on the first floor of the structure, a place you can explore very early in your adventure.