Serenity

Mystery Goo (満たされるしずく) is a material found in Kingdom Hearts that is used in Item Synthesis. They are said to bring feelings of contentment. Mystery Goo is used in the creation of several high level items, but perhaps most importantly is used in making Sora's Ultima Weapon.

Mystery Goos have one of the more unique, and perhaps one of the most frustrating, ways of dropping in the game. They will only drop from the three mushroom-type Heartless, and then only if certain conditions are met.

A higher level version, Mystery Force, appears in Kingdom Hearts: Final Mix.

White Mushroom
White Mushrooms are the most common mushrooms found in the game, but perhaps have the most annoying drop mechanism in the game. You always have a 10% chance of a Mystery Goo dropping upon appeasing a White Mushroom with three Magic spells. In order to increase the chances, you must cast the same spell three times in a row to satsify the Mushroom's demands; the chance of Mystery Goo dropping then increases to 20%.

Rare Truffles
Rare Truffles are appeased by being hit in air a certain number of times. The minimum times you must hit a Rare Truffle is ten times in a row; this gives you a 20% chance of recieving a Goo. Hitting one fifty times increases the odds to 40%, while one hundred times guarantees 100% a Mystery Goo will drop.

Black Fungus
Black Fungii have the most straightforward way of dropping Mystery Goos; you must defeat them with a Critical Hit. Due to their unique defense and way of fighting, this can be a tough thing to pull off. If Munny drops from a Black Fungus on the last hit, you are guaranteed a Mystery Goo as an item drop.

Mystery Force (満たされるチカラ) is a rare Item Synthesis material found in Kingdom Hearts: Final Mix. It is a more powerful version of Mystery Goo. Like its lesser counterpart, Mystery Forces are only dropped by a mushroom-type Heartless, in this case the gigantic Pink Agaricus. In order for a Mystery Force to drop, you must inflict a certain number of hits on a Stopped Agaricus before it unfreezes. Getting at least 40 hits in results in a 10% chance of a Mystery Force dropping. Getting 70 or more hits increases the odds to a 20% chance, while getting in at least 100 hits guarantees 100% that a Mystery Force will drop.

Mystery Forces are used in making two high-level items, the Ribbon and Sora's Ultima Weapon Keyblade.

Serenity (満たされる) is a type of material found in Kingdom Hearts II that is used in Item Synthesis. Serenity materials are special as they are one of three materials called "modifiers"; its use is not required in any synthesis recipe, but adding one to the recipe offers benefits. Serenity materials are arguably the most useful and most powerful of the three modifying materials because they create entirely new, upgraded items when added to a recipe. For example, a Drive Recovery can be upgraded to a High Drive Recovery with the addition of a Serenity Shard, or an armor such as Acrisius is upgraded to the more powerful Acrisius+ with a Serenity Stone.

In order to use Serenity materials, you must upgrade the synthesis Moogle to Level 3, Junior Moogle. The Serenity items are assigned a gold color to distinguish them from other materials.

Drops

 * Serenity Shard: Assault Rider, Creeper, Fat Bandit, Graveyard, Hot Rod, Large Body, Toy Soldier
 * Serenity Stone: Crimson Jazz, Devastator, Dusk, Living Bone, Morning Star
 * Serenity Gem: Dancer, Dragoon, Gambler, Sniper
 * Serenity Crystal: Assassin, Berserker, Samurai, Sorcerer

Other Conditions

 * Serenity Shard: Collect 50 different materials, obtain all Rank C materials.
 * Serenity Stone: Collect 100 different materials, obtain all Rank B materials, win the Pain and Panic Cup, chest in Jungle at Pride Lands.
 * Serenity Gem: Obtain 250 different materials, collect all Rank A materials, collect all Dense materials.
 * Serenity Crystal: Obtain 500 different materials, collect all Rank S materials, collect all Twilight materials.

Kingdom Hearts II: Final Mix + Changes
In this extended version of Kingdom Hearts II, Serenity Crystals no longer drop from enemies, making them extremely rare. They are instead made by synthesis, requiring Remembrance Crystals dropped by the rare Reckless Heartless, Tranquil Crystals dropped by the Mushroom XIII, and Bright Crystals.