Mystery Booster is a reprint set very different from others. It is by far the largest set with containing almost 2000 cards and was first released on November 7, 2019 at MagicFest Richmond. Each slot in a booster was one of 121 different cards. The high amount was chosen to evoke the feeling of not knowing what’s inside a pack and to provide players with a set that plays like Chaos Draft, however with synergizing mechanics. The chaos theme, which enables to gather cards from different eras, makes the reprint of both Disenchant and Naturalize possible.

For the first time, reprints were printed using their original card files. A planeswalker symbol on the bottom left indicates the cards are from a Mystery Booster.

There were four announced releases. The first one, labeled Convention Edition on the packaging, contained a subset of 121 fun cards in playtest card style. This print run was only available at conventions. The cards are dark. The second release, called WPN Edition or Retail Edition, was available in stores as of March 13, 2020 and had a subset of 121 foil cards which do not appear otherwise in the set. Some colors are brighter, whereas others remained the same. The third release, marketed as the second print run and available in mid 2020, was a short-term plan of Wizards of the Coast as an answer to the coronavirus recession: WPN stores received additional boxes at no charge as a financial support. In this print run, the planewalker symbols differ as follows:

— M15-framed cards:  smaller symbol

— older framed cards: larger symbol and rounded recess in the frame

— foils:  white, non-shiny symbol

On August 20, 2021,  another print run of the Convention Edition was released. While called so, it was delivered to WPN stores. The cards are glossy, show a prominently textured surface like in recent regular sets, and the playtest cards have no planeswalker symbol. Aside from that, some cards were swapped and some were duplicated on the sheets.