Synthesis

Synthesis is a recurring gameplay feature in the  series that allows new gear to be created from synthesis materials that are collected throughout the various worlds. Many of the most powerful pieces of equipment in the series, such as the Ultima Weapon, are obtained through synthesis. Moogles are experts in synthesis, so Moogle Shops are the domain of synthesis in many games.

Item synthesis
Item synthesis (アイテム合成) allows powerful items, weapons, armor and accessories to be created from synthesis materials collected across the worlds. New items are unlocked for synthesis by fulfilling certain criteria that vary from game to game. Each item can be synthesized as many times as desired so long as the required materials are available, except for the Ultima Weapon which can only be made once. Item synthesis can only be carried out at Moogle Shops.

Kingdom Hearts
Item synthesis can be carried out at the Item Workshop, located in Traverse Town above the Accessory Shop in the First District after using the green Trinity Mark in the Accessory Shop. The word "Mix" appears besides items that have already been synthesized at least once already. After every item has been synthesized at least once, Sora inherits the title of "Master Synthesist" from the moogle in the corner closest to the entrance to the workshop.

Every item informally belongs to a synthesis set, which progress in the power of the items and the rarity of synthesis materials. The first set is available upon accessing the workshop. Subsequent sets must be unlocked by synthesizing a certain number of unique items from the previous sets.

In Kingdom Hearts, there are 25 items in total that can be synthesized, which are grouped into five sets. Lists I-IV each contain six items, whereas List V only has Ultima Weapon. In Kingdom Hearts Final Mix, there are 33 items and six sets. Lists I-V each contain six items, whereas List VI is reserved for Ultima Weapon, Fantasista, and Seven Elements. Moreover, the new Encounter Plus ability is rewarded after 15 unique items are synthesized.

Kingdom Hearts II
Item synthesis can be accessed at Moogle Shops where resources and progress carries over across all worlds, despite Moogle Shops selling different items in different worlds. Each visit to the synthesis menu deposits all synthesis materials from Sora's inventory to the Moogle Shop.

Items can either be synthesized for the first time via Free Development or Recipes. Items from the former menu are unlocked by achieving Collector's Goals and upgrading the moogle's level, whereas items from the latter menu are attached to particular recipes that are obtained as rewards from chests and bosses. Items that have already been synthesized at least once appear in the Creations tab.

Kingdom Hearts II introduces special synthesis materials that may be added to recipes of the same rank to achieve certain modifications. Bright materials double the experience awarded to the moogle, Energy materials halve the amount of materials required, and Serenity materials can be used to upgrade some items into more powerful forms. Special materials can only be used upon reaching the appropriate moogle level. At level 4, two kinds of special materials may be used at the same time.

A Rank from C, B, A, or S is assigned to each synthesis material and synthesized item. Higher rank synthesis materials are generally rarer and used to make higher rank items that are more powerful and tend to award more synthesis experience. In order to use a special material in the synthesis of an item, the rank of the special material must match the item's rank.

In addition to receiving the items, item synthesis awards the moogle with experience, which increases the moogle's level. Levelling up grants perks, such as the ability to use special materials, halving the materials required for synthesis, and unlocking new items in Free Development.
 * Amateur Moogle (LV1) - Recipe and Free Development items can be created.
 * Novice Moogle (LV2) - Brightness or Energy Materials can be used in recipes.
 * Junior Moogle (LV3) - Serenity Materials can be used.
 * Skilled Moogle (LV4) - Two kinds of special materials (Brightness, Energy, or Serenity) can be selected at a time.
 * Senior Moogle (LV5) - Rank C items are at half-cost.
 * Artisan Moogle (LV6) - Rank B items are at half-cost.
 * Master Moogle (LV7) - Rank A items are at half-cost.
 * Superior Moogle (LV8) - The strongest items in Free Development are unlocked.
 * Primo Moogle (LV9) - Rank S items are at half-cost.

Kingdom Hearts III
Item synthesis can be accessed through the Workshop at any Moogle Shop. Synthesis materials from the stock are deposited to the Moogle Shop with each visit. All items are synthesized from a single menu with no marker present to distinguish items that have already been synthesized at least once. However, Jiminy's Journal lists every synthesized item under the "Synthesis" section and the "Synth Log" at the Workshop menu specifies the total number of unique items that have been synthesized.

Compared to Kingdom Hearts II, Kingdom Hearts III features a simpler synthesis system that omits recipes, special materials, and moogle levels. Instead, new items are unlocked for synthesis by completing Collector's Goals and Photo Missions.

Panel synthesis
Synthesis is available in Kingdom Hearts 358/2 Days in the form of panel synthesis. This feature is accessed through the Organization XIII-affiliated moogle, who is found in the Grey Area of the Castle That Never Was and, after Roxas leaves the Organization, Twilight Town.

The synthesis of a panel requires certain ingredients and some munny. In addition to material panels, which replace traditional synthesis materials, ingredients may also include item panels, magic panels, and ring panels. Recipes reappear, but they do not unlock new panels for synthesis, rather recipes are a form of material panel that are consumed in the synthesis of some panels.

New panels are unlocked for synthesis by progressing through the game to upgrade Roxas's rank. Each time Roxas is promoted within the Organization, the moogle offers new items for sale and synthesis. In addition to requiring a certain rank, some items are only unlocked once certain materials needed for their synthesis are collected. For example, many Gears become available after the appropriate Gear Component is acquired.

Throughout the story, Organization XIII members hanging around the Grey Area occasionally ask Roxas to synthesize particular panels for them, sometimes even providing some necessary ingredients. Completing these optional tasks results in small rewards, typically rare material panels. These tasks can only be completed on the days they are given; they cannot be completed after progressing the story further.

Kingdom Hearts χ
Each Keyblade begins in their base form, equivalent to level 0, and can be upgraded to a maximum of level 50. The appearance of a Keyblade changes as it evolves and certain level milestones are reached. Raising a Keyblade's level requires synthesis materials, most of which are typically found in the world of the Keychain's origin. The rarest materials, however, are mainly obtained from limited-time events or purchased with premium currency.

In Kingdom Hearts χ, Keyblades are upgraded from the Keyblade menu. Levelling a Keyblade offers better and increases its Keyblade Bonus. A Keyblade's appearance can change up to a maximum of five times.

In Kingdom Hearts Union χ, Keyblades are upgraded from the Equipment menu. Levelling a Keyblade increases the boosts associated with particular medal slots. New medal slots entirely, including Upright and Reversed slots, are unlocked at specific levels. Additionally, each Keyblade level up increases the Special Attack Gauge and Friend bonus. A Keyblade's appearance can change up to three times in total.

Kingdom Hearts III
Keyblades can be upgraded at The Keyblade Forge, which can be accessed through the Workshop at Moogle Shops. Each Keyblade starts at a level ranging from 0 to 10 when it is obtained; upgrading to higher levels boosts the Keyblade's strength and magic, and unlocks that are active when wielding it. The max level of every Keyblade is 10.

Raising the level of a Keyblade requires particular synthesis materials, unique to that Keyblade. Rarer materials are needed for higher levels and stronger Keyblades. In order of increasing rarity, Fluorite, Damascus, Adamantite, and Electrum are materials that are strongly tied to Keyblade upgrades as each level upgrade requires one of these materials. The synthesis materials used at the Keyblade Forge are shared with those used in item synthesis.

Room Synthesis
In Kingdom Hearts Chain of Memories, new rooms are created at doorways using map cards, which are obtained from enemies. The type of room created depends on the map card used. A doorway may have certain criteria on which map cards can be used on it, such as a specific colour or high value. Map cards that satisfy certain conditions must also be used for special rooms that are opened with a keycard.

Command Meld
Instead of a traditional synthesis system accessed through moogles, Kingdom Hearts Birth by Sleep features the Command Meld system, where new s can be created by combining specific pairs of deck commands. Most deck commands must first be mastered before they can be used as ingredients. Synthesis materials may be added to the mix to attach to the resulting command.

Although the Command Meld menu lists any pairs of compatible Commands at all times, the resulting Command is not listed until the appropriate Recipe is obtained. Unlike in other games, any command can be melded without its recipe; the recipe simply shows what the resulting command will be before melding occurs. Command Meld can be done anywhere through the field menu and does not need to be carried out at a particular workstation.

Ice Cream mixing
In Kingdom Hearts Birth by Sleep, ice cream commands can be made at the Ice Cream Shop in Disney Town from flavors collected from Prize Pods. Each ice cream is made from different flavors and can only be created after its respective Command Style is unlocked. After an ice cream has been created once, it also becomes available for sale. The Sweetstack Keyblade is obtained after all ice creams are made.

Command Conversion
Kingdom Hearts Re:coded features the Command Conversion system, which can be accessed from the Command Matrix in the field menu. A pair of commands can be converted into a single, new, similar to the Command Meld system from Birth by Sleep. The main difference is that the new command is usable as soon as the pair of commands are put together, a feature known as "test-conversion". It is only after the ingredient commands accumulate enough Command Points (CP) that they can be permanently converted into the new command, after which the substituent commands are destroyed. A converted command may receive an Overspec bonus of gaining extra levels and filling the Clock gauge quicker, and/or having a faster reload time.

Spirit creation
In Kingdom Hearts 3D: Dream Drop Distance, synthesis revolves around the creation of new Spirits, since s are mainly obtained from chests, shops, and Ability Link boards. Spirits can be created at any point from the field menu.

The creation of a Spirit requires certain Dream Pieces, which act as synthesis materials. Unlike previous games, the amount of materials needed in a particular synthesis is not fixed. Rather, a larger number of Dream Pieces may be used to create a Spirit to raise its rank and starting level. Additionally, a Deck Command may be used as an ingredient when making a Spirit to provide a particular stat boost to the Spirit.

There are many combinations of Dream Pieces that can be used to make Spirits and these combinations can be used at any point in the game, provided the required Dream Pieces are available. Only a silhouette of the resultant Spirit is shown before it is created, unless the appropriate Recipe has been obtained. Some combinations of Dream Pieces give two possible Spirits as outcomes.

Cooking
In Kingdom Hearts III, Sora and Remy can cook food at Le Grand Bistrot, which is in Twilight Town, but can also be accessed from Save Points. Each dish is cooked from different ingredients that are obtained from props and Flan throughout the worlds. One of five brief minigames must be completed each time that a dish is cooked, although multiple servings of the same dish may be made in one go. Depending on the performance during the minigame, Sora may obtain nothing, standard versions of the dish, or improved ★★★ versions.

Cooking new dishes awards stars to the Bistrot. Dishes belong to two menus: the "Classic Menu", available from the start, and the "Special Menu", which is unlocked after enough stars are awarded. The Grand Chef Keyblade is obtained after the Bistrot is awarded five stars. Dishes that have been cooked before are listed in the "Recipe Collection" tab of Gummiphone.