In Persona 3 Reload, major Arcana Cards are cards you can pick during Shuffle Time. These cards can grant you various bonus effects. Although, note that some effects will last only until you leave Tartarus. Major Arcana Cards can be obtained from defeating bosses or from the passages in the Monad.
Defeat the Full Moon Bosses
A major arcana card will be rewarded to the player after they have defeated a full moon boss. Since each boss is tied to a major arcana, you will have to beat them all to gell all the cards.
Defeat the Monad Passage Bosses
Once you reach a certain point in the story, you will unlock the Monad floors that contain several bosses with a major arcana card. You can find these bosses at the Monad Passages.
Get All Major Arcana Cards for an Arcana Burst
You can get an Arcana Burst if you get all of the Major Arcana Cards you have unlocked so far during your run in Tartarus. When you do, you will gain a bonus Shuffle Time and all of the cards will be higher ranked until you leave Tartarus.
