Arcana

An arcanum is a card or playbook insert, something you give the players. Each one represents a discovery—an artifact, a place, a bit of lore, a magical effect, etc.— with mysteries that the PCs can unlock. "Arcanum" is a game term; it's not something characters are likely to refer to in-fiction.

The front of an arcanum describes what the PC can tell at a glance or with a little effort, plus the requirements for unlocking its mysteries. The back shows those mysteries, which can include custom moves, new options, followers, and consequences.

Minor arcana are small cards, like the one shown here. They provide no real benefit until the PC unlocks them. Once unlocked, the PC gains access to all the benefits on the back.

Major arcana are half-page playbook inserts; see Noruba’s Ice Sphere for an example. Each offers one or more "free" custom moves. A PC who unlocks its mysteries gains more powers, but using those powers has consequences.

Stonetop includes 64 minor and 18 major arcana by default. All of these are reproduced in appendices c and d of Book II.

The Seeker playbook starts with a major arcanum and two minor arcana. The Heavy starts with Storm Markings if they take the Storm-marked background.