While you're somewhere near the northern mountain range of the overworld area where Castle Advent is on, you're bound to stumble upon two thieves talking about some stolen goods. When one thief asks the other where it's located, the other says that it's hidden somewhere on the continent, past the bridge that leads to the Bewildering Wood. The hero will note this clue down as Stolen Goods Cache #1, which you can revisit in your key items section.
Related: How to solve Monster Memo #1 in Voice of Cards: The Isle Dragon Roars
The location is easy to find. Just walk to the eastern edge of the continent where the entrance to the Bewildering Wood is located. But instead of entering the Bewildering Wood, walk south past the bridge. The treasure is on the second-to-the-last tile of that column.
You see something within a tree's hollow and take a closer look. Sure enough, the game tells you that you've found the location! It contains a Steel Breastplate, which can be equipped by Mar (and Ridis if you already have her in your party).
For more help with Voice of Cards: The Isle Dragon Roars, Pro Game Guides has you covered.
Bianca has over three years of experience in gaming journalism, specializing in anything remotely turn-based and strategic, like Pokémon, Final Fantasy, and Honkai: Star Rail. She's a huge fan of Square Enix, RPGs, party games, and visual novels, but will play anything with a banger OST. She's a proud early bird.