Kingdom Hearts χ[chi]
When Player first arrives in Daybreak Town, Chirithy explains that cards (or fragments (フラグメント, furagumento?)) are needed to draw out the power of the Keyblade. Shortly after, a moogle bestows Player with their first set of cards.
The cards are divided into Attack cards and Assists cards and can be categorized by rarity, which spans from normal (N/N+) to rare (R/R+) to super rare (SR/SR+), by card type, or by alignment.
Attack cards (アタックカード, Atakku kādo?) determine Player's attack and defense values. There are three types: Power (パワー, Pawā?), Speed (スピード, Supīdo?) and Magic (マジック, Majikku?), each with a different set of abilities and preferred by certain Keyblades, increasing their attack values momentarily. A full attack deck consists of nine cards.
Cards with a rarity of R+ and better can be imbued with certain skills to expand their abilities or increase their stats. Newly released cards will be boosted for a set period of time.
The alignment is mostly a cosmetic value that does not make much difference in the main portion of the gameplay, while it can trigger an additional damage boost called EX Card Bonus (EXカードボーナス, EX kādo bōnasu?) during raids when using the correct Keyblade with the corresponding cards. The standard cards that the game was released with are called Upright cards (アップライトカード, Appuraito kādo?) and only depict the heroes and supporting characters with a bright yellow and gold color scheme, while the Reverse cards (リバースカード, Ribāsu kādo?) only show the villains and enemies in a dark blue and purple color scheme.
List of Cards
New Attack cards are released in a two-week cycle, while new Assist cards are only released every four weeks. Usually, these cards will be boosted until the next cycle, meaning their stats are multiplied by a factor for this time. Normally, the factor is tied to the rarity of the cards; the stats of R+ cards will be multiplied by 1.5, stats of SR cards by 2, and stats of SR+ cards by 3. Occasionally, SR+ cards' stats are also multiplied by 4.
It is also possible to boost cards by yourself using special Fairy Godmother cards. This boost will last a week and is also tied to the rarity of the Fairy Godmother card. A boosted card cannot be boosted again, as long as it is affected by the first boost.
Depending on the card's rarity, it can level up a certain number of times to improve its stats. The only way to achieve this is by fusing another card with it.
The amount of experience points gained from these material cards is, again, dependent upon the rarity, the level of the used cards, and the cards' type. For example an R+ card will provide more experience than an N card, while a card that is already at a certain level will also give more experience than a card at level 1. Using a material card of the same type as the base card to level up (e.g. using a Speed card to level up another Speed card) will result in a 1/5 experience boost. Furthermore, there are special Moogle cards which will provide a huge EXP boost.
Each material card that is used for synthesis costs a specific amount of Munny, which is tied to the card's level. Occasionally, the game will half the synthesis costs or double the received experience from material cards for a limited amount of time.
Limit Cuts and High Purity
When the card reaches its maximum level, it cannot be leveled up further without using Limit Cuts (リミットカット, Rimitto katto?). To Limit Cut a card, it has to be synthesized with a duplicate of this card or, alternatively, with a Yen Sid card of the same rarity. Each Limit Cut raises the maximum level of the base card by 5; the maximum number of Limit Cuts is once again depended on the rarity of the card.
When a card hits its maximum level after all Limit Cuts have been used up, it reaches High Purity (ハイピュリティ, Hai pyuriti?); its background is changed to a rainbow-colored one, and it receives a permanent stat boost.
Ultimate cards and Rebirth
If an SR+ card has been "high purified," it can become an Ultimate card (アルティメットカード, Arutimetto kādo?). To ultimise a card, three Gems (魔石, Maseki?) are needed, with their nature being dependent upon the card's type and alignment.
An Ultimate card receives a fourth skill slot, a new border, and it can be synthesized with other SR+ material cards to transfer a randomly chosen fraction of their stats to the Ultimate card. This can only be done a definite amount of times, and once this number is reached, the Ultimate card can go through Rebirth (転生, Tensei?). A Rebirth of an Ultimate card once again requires Gems and lowers the stats of the card to the original High Purity stats plus a set fraction of the collective transferred stats, but it also allows Player to synthesize the cards with even more SR+ material cards for an even higher amount of times and higher maximum stats.
There is also the option to reset a card to its original High Purity stats and number of Rebirths with a Remembrance Gem (おもいでの魔石, Omoide no maseki?). Using it also provides Player a certain number of Moogle material cards for each time stats were transferred to the Ultimate card.
To reach the maximum stats of the Ultimate Card, it is essential to use highly boosted SR+ material cards instead of unboosted ones and boost the Ultimate Card before it is going through Rebirth to increase the fraction of stats that will be reduced.
Player can earn new cards by defeating Heartless, opening chests, trading Medals, or performing card draws by using Mog Points, Tickets, or Charge Munny. Often, timed missions or actions will also reward Player with limited cards.