12 collector boosters:

The Kaldheim Collector Booster features 11 traditional foil cards (and a double-sided foil token in addition), 5 special alternate-frame cards, and a combination of 5 rares/mythic rares. Let's take a closer look at the breakout of each Collector Booster in addition to the 5 foil commons/common snow dual lands and 2 foil uncommons found inside.

1 Rare Saga – A thematic Kaldheim rare that isn't found in draft boosters, or one of the Kaldheim Commander Deck rares or mythic rares—see the section on Sagas above for more about this slot.

"When we decided to create a set that features snow, especially a Viking-inspired world, it made sense to give snow focus. In Magic's history, we've done snow a few times before. We decided the gameplay was going to be better if you could quickly scan to count your snow permanents in the same way we distinguish artifacts and enchantment creatures. I focused on creating a concept that maintained color identity while also being flavorfully "snow."

1 Extended-art card – One of 36 extended-art rares and 4 extended-art mythic rares. Each rare shows up twice as often as each mythic rare.

1 Foil rare or mythic rare – This slot features the 64 rares and 20 mythic rares that you can find in the main set of Kaldheim (so you won't find Commander cards or the thematic Kaldheim rare cards here).

1 Non-foil and 1 foil showcase uncommon – These can be 12 different legendary cards, each featuring the showcase Viking frame.

1 Foil rare or mythic rare with a showcase, borderless, or extended-art frame – The best way to finish off your Collector Booster experience is with the best of the best. Here you will find a Booster Fun treatment that captures all the awesomeness of Kaldheim in traditional foil! There are 54 rares and 20 mythic rares available in this slot...

Read more: https://magic.wizards.com/en/articles/archive/feature/collecting-kaldheim-2021-01-07