The TEST Set is the first official booster pack set made for Death of Kings. This test wasn't and never will be released, as it contains cards that were printed as a test, and may contain different card texts, images, fonts, font sizes and names.
Booster Pack Edit
The Booster Pack for the TEST Set is a Mini-Pack. It contains 3 cards and no guaranteed rarity. If the pack does contain an Uncommon or higher card, it will only be one (and the rest Common).