A set of three Promo cards for The Lost Expedition was released at UK Games Expo 2017 and available at other US events in 2017. They're designed for solo game but work with the co-op game.
All 3 Promo cards are shuffled into the main deck, and they each provide a greater risk for a greater reward.
The three cards are:
99.5 Ancient Trap!
40.5 Golden Idol!
For more information, visit the BGG listing.