Mysterious Trading Cards are back! This time for the Steam Holiday Event 2019
The sale has not started yet, this time the sale starts on December 19, 2019.
The set contains 8 cards with Steam Award theme.
Mysterious Trading Cards: Steam Holiday Event 2019
Currently the only way to get a mysterious Tradingcard is by crafting a badge. Instead of the regular coupon you'll get a Mysterious Tradingcard with a chance of it being a Foil one.
If you use cards to craft a badge that are restricted from being traded or sold (e.g. because you bought them recently) it will apply the restriction to the Mysterious Tradingcards with the same timeframe as well.