Set boosters are a new way of opening MtG packs that you don't intend to draft! The idea behind these packs is to have more of the things that players think are cool. They have 12 cards per pack guaranteed and there could be a special 13th card from "The List." The list is a set of carefully curated cards in all rarities that appear in one out of approximately every 4 packs.
There are 4 chapters in the pack: Welcome, Fireworks, Big Finish, Epilogue.
The Welcome chapter includes an art card, a land card, and 6 connected common/uncommon cards.
Fireworks includes a "head-turner" slot and two wildcard rarity slots.
The Big Finish includes a guaranteed rare/mythic rare slot and a foil card slot.
The Epilogue is a slot that will contain either a token card or a card from the list.
Each slot has the chance for something special. E.g. the art card slot can have a "Signature Art Card" with the artist's signature embossed in gold.