Treasure hunts are often surprisingly difficult to discover outside the country in which they take place. Here in France, we hear relatively little about hunts organized in the United Kingdom, the United States, or elsewhere. The same is probably true abroad for French treasure hunts. I would therefore like to introduce MYSTERIOSA, a new hunt currently taking place in France, built around an illustrated book containing eleven puzzles and a unique golden prize valued at €50,000.
After publishing two articles about MYSTERIOSA in French, I have brought together the most useful information in this shorter English overview. The aim is to explain what the hunt is, what participants are looking for, and what is currently known about the book, the prize, and the rules.
What Is MYSTERIOSA?
MYSTERIOSA is a French treasure hunt launched on June 4, 2026, by Éditions du Trésor. It is based on an illustrated book of around 120 pages containing stories, artwork, hidden clues, and eleven puzzles. Solving them should eventually lead participants to a chest hidden somewhere in France.
The hunt is aimed primarily at adults because of the announced difficulty of its puzzles. Although players are free to discuss their observations and compare theories, participation remains individual. Only one person can officially claim the treasure and submit a complete solution to the organizers.
Twelve contributors (French-language article) took part in creating the literary and visual content of the book. Eleven of them wrote ten original chapters, with one chapter created by two authors. The subjects include Atlantis, Rennes-le-Château, the Voynich manuscript, Sherlock Holmes, and the Père-Lachaise columbarium. A twelfth contributor, Mathilde Payen, created a black-and-white comic.
These stories and illustrations are not simply decorative. Clues are hidden throughout the book, and reading the complete work is necessary to solve the eleven puzzles presented at the end. The puzzles themselves were created by an anonymous author using the pseudonym Bastien Lebaudy.
If some of the puzzles involve codes, ciphers, extraction methods, or similar mechanisms, the AppErgo code and decoding tools may also be useful for testing different approaches.
A Unique €50,000 Treasure
The prize is not simply a cash reward. According to the official rules of MYSTERIOSA, it is a unique sphere made from 18-carat gold and set with several diamonds. It was created in 2026 by French craftswoman Camille Orfèvre and was valued at €50,000 at the time of purchase.
The golden sphere is not buried directly inside the hidden chest. The person who finds the chest must follow the identification procedure contained inside it, contact the organizers, provide the requested personal details, and explain in detail how the puzzles were solved.
The treasure will only be awarded after both the discovery and the proposed solution have been validated. Finding the chest alone may therefore not be sufficient if the claimant cannot demonstrate how the clues and puzzles led to its location. Once a winner has been officially confirmed, the prize must be awarded within a maximum period of three months.
An Experienced Publisher and a Successful Launch
MYSTERIOSA is not the first treasure hunt organized by Éditions du Trésor. The publisher previously created Le Trésor perdu, found in 2018, L’Or de Sipán, found in 2022, and Le Trésor de l’île au Crâne, found in 2025. This experience probably helped attract participants who were already familiar with its previous games.
Before publication, MYSTERIOSA was offered through a crowdfunding and preorder campaign on Ulule. The initial objective was 350 preorders, but the campaign ended on May 7, 2026, with 1,518 preorders from 814 contributors. This represented 433% of the original target.
Some supporters also received additional rewards, including a mysterious puzzle piece presented as a clue. The campaign was not intended to finance the treasure itself, which had already been funded before the campaign began. The money was mainly used to support production of the book and, after the initial target was exceeded, a wider media campaign.
How the Treasure Hunt Works
The hunt began on June 4, 2026. It will end as soon as a winner is officially confirmed or, at the latest, on June 5, 2028, at midnight French time. Participants therefore have approximately two years to solve the book and locate the hidden chest.
The claimant must provide the information requested inside the chest and submit a detailed account of the method used. The organizers will then examine the solution and verify that the discovery resulted from solving the puzzles. Once all the required elements have been accepted, a winner can be officially declared.
Although participants may exchange observations, theories, and partial solutions, only one person can officially claim the treasure. Anyone working within a group must therefore decide who will submit the final solution if the chest is discovered.
A French Hunt Still Little Known Abroad
Despite the value of the prize, the success of the Ulule campaign, and the involvement of several well-known contributors, MYSTERIOSA has so far received relatively limited media coverage. French publications including Actu.fr and Livres-jeux.fr have covered the hunt, and a literary segment was also broadcast by Europe 1. However, the project does not yet appear to have reached a very broad audience.
This is one reason for publishing an English article. Treasure hunts often remain confined to their country of origin because most of the available information is published only in the local language. French treasure hunters may know little about hunts taking place in Britain, the United States, or elsewhere, while international communities may never hear about new French projects.
Several French-speaking websites and communities already allow participants to follow the latest news and discuss possible solutions:
- the official MYSTERIOSA page on the Éditions du Trésor website;
- the official MYSTERIOSA rules (in French);
- the official MYSTERIOSA Facebook page and the Éditions du Trésor Facebook page;
- the MYSTERIOSA section of the Ultima Forsan forum;
- the Relais de Chasses Discord server, which requires a Discord account;
- the MYSTERIOSA page on Chasses-au-tresor.com.
Chasses-au-tresor.com is one of the main French-language resources for discovering current treasure hunts and following their progress. It was also through this website that I first discovered MYSTERIOSA.
MYSTERIOSA combines literary stories, illustrations, hidden clues, and eleven final puzzles in a project supported by an experienced publisher. Whether it will become known beyond France remains to be seen, but it already offers international treasure hunters a glimpse of a new hunt currently unfolding here, with a real chest to find and a unique golden reward waiting for the person who can solve it.
MYSTERIOSA is presented on the official MYSTERIOSA page on the Éditions du Trésor website. The book is also available from Fnac and Amazon France.