Mystery Cards are cards that you can received by crafting steam card sets starting from a week before the sale start date. In this year, for 2018 Summer Sale, you can receive Mystery Cards from June 14 at 9:55 a.m. PT until June 21 at 10:05 a.m. PT.


You can receive Mystery Cards by crafting any steam card sets from June 14 at 9:55 a.m. PT until June 21 at 10:05 a.m. PT. You can buy them for CS:GO and TF2 keys through card bots like this one.


When the Steam Summer Sale 2018 starts, all Mystery Card will be converted to a Summer Sale Cards. Until then those cards cannot be crafted into summer sale badge. Steam Summer Sale 2018 starts on June 21 at 9:55 a.m. PT and runs until July 5 at 10:05 a.m. PT.

You can craft 2018 Steam Summer Sale Badge since the sale start date, from June 21 at 9:55 a.m. PT. Usually, Steam allows users to craft those badges one month after the sale ends, but now there are is new information about it.

There are multiple things that you can do with Steam sale cards:

1.You can trade them for CS: GO keys through trade bots like this one.
2.You can sell them on the steam community market.
3.You can create a badge from them when the sale starts.
4.You can craft them into gems, which is the least profitable option.