The Panel System is the system in Kingdom Hearts 358/2 Days through which characters upgrade weapons and stats, equip armor and accessories, gain abilities, and use Magic.
There are several types of panels, with different functions. Each panel must be installed in a grid in order to take effect. The grid begins with fifteen open slots, and additional slots are unlocked by obtaining Slot Releasers. There can only be one weapon panel and one ring panel installed in the grid at one time, and multiple ability panels cannot be installed with the same name; otherwise, the panels that can be installed are restricted only by the size of the grid and the size and shape of the panels.
Some panels take up multiple slots. These panels have link zones, where certain panels can be placed to "link" with the main panel for additional effects. For example, Doublecast ④ occupies four slots in the grid, including a link zone that covers three slots, in which magic panels can be installed. Each magic panel in that link zone will grant two casts of its respective magic during missions.
A Slot Releaser (スロット開放 Surotto Kaihō ) is a single-use item that unlocks an additional slot in the panel grid. It is automatically used immediately after it is obtained.
There are 105 Slot Releasers that can be obtained, bringing the grid to its full 120 slots.
- 76 Slot Releasers are obtained by completing missions, from Mission 14 onward. The four exceptions are missions not assigned by Organization XIII:
- Seven Slot Releasers are obtained by redeeming Challenge Sigils at the Moogle Shop.
- 5 Challenge Sigils
- 30 Challenge Sigils
- 50 Challenge Sigils
- 80 Challenge Sigils
- 130 Challenge Sigils
- 190 Challenge Sigils (Legend)
- 250 Challenge Sigils (Legend)
- Six Slot Releasers are obtained by redeeming Mission Crowns at the Moogle Shop:
- 1 Mission Crown
- 20 Mission Crowns (Rookie)
- 45 Mission Crowns (Agent)
- 65 Mission Crowns (Expert)
- 85 Mission Crowns (Master)
- 280 Mission Crowns (Legend)
- Seven Slot Releasers can be purchased from the Moogle Shop:
- One can be purchased upon reaching Novice rank for 270 Heart Points.
- One can be purchased upon reaching Rookie rank for 1200 Heart Points.
- One can be purchased upon reaching Agent rank for 1650 Heart Points.
- One can be purchased upon reaching Expert rank for 3000 Heart Points.
- One can be purchased upon reaching Master rank for 4000 Heart Points.
- Two can be purchased upon reaching Legend rank, one for 10000 Heart Points and one for 50000 Heart Points.
- Nine Slot Releasers can be found in chests during the following missions:
- Mission 19: Eliminate the Deserters
- Mission 35: Collect hearts
- Mission 47: Collect hearts
- Mission 56: Eliminate both giant Heartless
- Mission 61: Vanquish the Heartless threat
- Mission 70: Eliminate the Deserters
- Mission 81: Eliminate the Emerald Serenade
- Mission 85: Collect hearts
- Mission 88: Eliminate the giant Heartless
List of Panels
Item Panels 
Item panels, when installed, provide consumable items at the start of a mission. These items are separate from the backpack, which has a limited capacity; there is no limit to the number of item panels that can be equipped. If the item is consumed during a mission, the panel is consumed, as well.
Support Panels 
Support panels have three types, one which raises the character's level, and one which increases the amount of items that can be picked up from treasure chests or enemy drops during a mission. The final type unlocks characters and modifiers to Mission Mode and does not appear in the inventory.
Magic Panels 
- See also: Magic Panel and Magic
Equipping magic panels allows magic to be used during missions. Basic magic panels may be installed individually to grant a single cast of magic each, or they can be placed in the link zones of special magic panels, either granting multiple casts, or increasing the potency of the magic. The effects are cumulative: for example, linking one Fire panel to Doublecast and two to Magic LV2 will grant four casts of Fire LV4, while linking two Fire panels to Triplecast and one to Magic LV3 will grant seven casts of Fire LV3.
Magic panels are not consumed when magic is cast. Used casts can be replenished by using items like Ethers or Elixirs.
Ability Panels 
- See also: Abilities (KHD)
Installing ability panels activates corresponding abilities. Some abilities can be activated by multiple panels, with the difference being the size of their link zones, but only one panel can be installed for a single ability. Many ability panels have associated link panels that level up the main panel's associated ability or provide additional abilities. For example, linking Glide LV+ Ⓛ and Homing Glide Ⓛ to Glide ③ provides the Glide LV2 and Homing Glide abilities.
Weapon Panels 
Weapon panels modify a character's weapon, with Gears changing it to a new form, with unique attack combos and stats, and Unit link panels further boosting stats and unlocking abilities. While each weapon has a different set of stats, groups of gears will provide weapons with similar stat balances. Each playable character's weapon will be affected by Gears and Units differently. Only one Gear can be equipped at a time.
Ring Panels 
Ring panels are accessories that may provide stat boosts, equipment abilities, or resistance to status effects. Only one ring panel can be equipped at a time.
- See also: Panel synthesis
Material panels cannot be installed in the panel grid. Instead they are used at the Moogle Shop to synthesize other panels.