Magic may refer to a value provided by certain Gear or a type of card that can be added to decks.
The Magic entry gives a value that determines the total number (and/or strength) of Magic cards that can be shuffled into the corresponding deck. Magic cards each have a Magic value on them; the total value of all Magic cards in an individual deck must not be greater than the highest individual Magic entry on the corresponding Gear card (for which the PC meets the level and training requirements). The highest Magic Enchantment need not be on an equipped Gear card; however, for Rituals and Augments, use the Magic entry for the currently equipped Ritual and Augment respectively.
If Magic values change inside a scenario for any reason, the PC cannot make any adjustments to their deck until after the scenario ends, and any included Magic cards may still be played even if the PC now has insufficient Magic to have included the card. Immediately after the scenario ends, or whenever Magic values change outside of scenarios, the PC may make adjustments to the affected deck or decks. In the case of Magic increasing, changes are optional; in the case of Magic decreasing, changes are mandatory if the affected deck has Magic requirement totals that exceed the new Magic value.
When decks are modified as a result of Magic changes, the player can only change included Magic cards. Other cards may still only be changed as a result of a rest or level increase, as normal. The sole exception to this is if a player's deck is reduced below the allowed minimum as a result of having to remove Magic cards. In this case, and only in this case, the player must add other (valid) cards up to (but not beyond) the deck's minimum until a rest or level up event occurs.
A Magic card is a special type of card that can only be added to a PC's deck if the PC has enough Magic available to include the card. Each Magic card lists the required Magic (in place of the usual level requirement on a card). See the preceding section for more information.
Magic cards may be any type of card - Action, Reaction, Strategy, Assist, or Interrupt. Magic cards are specific to a single type of scenario and can only be included in the corresponding deck (using the corresponding Magic value).
Magic cards also have an Extra Effect provided, which adds some additional magical options when including the card into a deck. Since finding the card in a deck can be cumbersome, it is recommended for a player to note down any Extra Effect they include in their decks that they may wish to use. Unless otherwise specified, Extra Effects may be used within scenarios, and you don't need to have the card in hand to use them; however, you are still limited to one use each per rest.
For more information, see Player's Guide Chapter 7: Gear and Wealth.