This promo was originally featured in the Brettspiel Adventskalender 2018 for day 25.
Castles of Burgundy "Solo" is a mini expansion including 1 double-sided board. Requires the base game to play.
Note: If you own the 2019 20th's anniversary edition (with the updated artwork), then you also have a version of this solo board that matches that edition. This 10th expansions matches the artwork of the standard, non-anniversary edition.
For more information, visit the BGG listing.