Hungry

Serenity (満たされる), also dubbed as "Mystery" in Kingdom Hearts, is a material type available in Kingdom Hearts and Kingdom Hearts II. Serenity materials contain the essence of fulfillment, and are colored gold. In Kingdom Hearts they are used as normal synthesis items, while in Kingdom Hearts II they are "modifier" materials that can be added to a recipe of the same rank to upgrade it to a more powerful form, and are usable once the Moogle reaches level 3, Junior Moogle. In Kingdom Hearts II, once all Serenity materials are obtained the Moogle will reward Sora with a Magic Boost.

Kingdom Hearts

 * Mystery Goo (満たされるしずく): Black Fungus (20%), Rare Truffle (20%/40%/100%) , White Mushroom (10%/20%)

Kingdom Hearts Final Mix introduced the Mystery Power (満たされるチカラ), dropped only by the Pink Agaricus (10%/20%/100%).

Kingdom Hearts II

 * Serenity Shard: Assault Rider (4%), Creeper (2%), Fat Bandit (4%), Graveyard (4%), Hot Rod (4%), Large Body (4%), Toy Soldier (4%)
 * Serenity Stone: Crimson Jazz (4%), Devastator (4%), Dusk (2%), Living Bone (4%), Morning Star (4%)
 * Serenity Gem: Dancer (4%), Dragoon (4%), Gambler (4%), Sniper (4%)
 * Serenity Crystal: Assassin (4%), Berserker (4%), Samurai (4%), Sorcerer (4%)

Kingdom Hearts II Final Mix

 * Serenity Shard: Assault Rider (4%), Creeper (2%), Fat Bandit (4%), Graveyard (4%), Hot Rod (4%), Iron Hammer, Large Body (4%), Silent Launcher, Toy Soldier (4%)
 * Serenity Stone: Aerial Champ, Air Viking, Crimson Jazz (4%), Devastator (4%), Dusk (2%), Living Bone (4%), Morning Star (4%)
 * Serenity Gem: Dancer (4%), Dragoon (4%), Gambler (4%), Mad Bumper, Reckless, Sniper (4%)
 * Serenity Crystal: Bulky Vendor (100%).

Kingdom Hearts II

 * Serenity Shard: Obtain a total of 50 materials; obtain all Rank C materials; chest at The Cave of Wonders: Treasure Room.
 * Serenity Stone: Obtain a total of 100 materials; obtain all Rank B materials; win the Pain and Panic Cup; chest at the Jungle.
 * Serenity Gem: Obtain a total of 250 materials; obtain all Rank A materials; obtain all Dense-type materials.
 * Serenity Crystal: Obtain a total of 500 materials; obtain all Rank S materials; obtain all Twilight-type materials.

Kingdom Hearts II Final Mix

 * Serenity Gem: Two chests at Cavern of Remembrance: Mining Area.
 * Serenity Crystal: Obtain all Remembrance-type materials; obtain all Tranquil-type materials; complete the "Heart" puzzle; chest at the Cavern of Remembrance: Mining Area; chest at the Cavern of Remembrance: Engine Chamber.

Kingdom Hearts II Final Mix
Serenity Crystals can be synthesized through Free Development once the Moogle reaches level 8, Superior Moogle. Their upgrade is the Manifest Illusion recipe.
 * 1 Tranquil Crystal
 * 1 Remembrance Crystal
 * 9 Bright Crystal

Kingdom Hearts
Serenity materials are used to synthesize the following items:
 * Power Up (1 Mystery Goo)
 * Defense Up (1 Mystery Goo)
 * Atlas Armlet (1 Mystery Goo)
 * Ultima Weapon (3 Mystery Goo)

Kingdom Hearts Final Mix
Serenity materials are used to synthesize the following items:
 * EXP Earring (1 Mystery Power)
 * Mythril (1 Mystery Goo)
 * Three Stars (3 Mystery Goo)
 * Atlas Armlet (1 Mystery Goo)
 * Ribbon (3 Mystery Power)
 * Ultima Weapon (5 Mystery Goo, 3 Mystery Power)

Kingdom Hearts II
Serenity materials are used to synthesize the following items:
 * Megalixir (1 Serenity Gem)
 * Mega-Ether (1 Serenity Stone)
 * High Drive Recovery (1 Serenity Shard)
 * Magic Boost (1 Serenity Crystal)
 * Power Boost (1 Serenity Crystal)
 * Firagun Bangle (1 Serenity Shard)
 * Blizzagun Armlet (1 Serenity Shard)
 * Thundagun Trinket (1 Serenity Shard)
 * Chaos Anklet (1 Serenity Shard)
 * Acrisius+ (1 Serenity Stone)
 * Buster Band (1 Serenity Stone)
 * Diamond Ring (1 Serenity Shard)
 * Orichalcum Ring (1 Serenity Shard)
 * Fencer Earring (1 Serenity Stone)
 * Slayer Earring (1 Serenity Stone)
 * Master's Ring (1 Serenity Gem)
 * Mythril Stone (1 Serenity Shard)
 * Mythril Crystal (1 Serenity Stone)
 * Ribbon (1 Serenity Gem)
 * Star Charm (1 Serenity Gem)
 * Save the Queen+ (1 Serenity Crystal)
 * Save the King+ (1 Serenity Crystal)
 * Ultima Weapon (7 Serenity Crystal)

Kingdom Hearts II Final Mix
Serenity materials are used to synthesize the following items:
 * Lost Illusion (1 Serenity Gem)
 * Lucky Ring (1 Serenity Crystal)
 * Freeze Pride+ (1 Serenity Crystal)
 * Centurion+ (1 Serenity Crystal)
 * Shade Archive (3 Serenity Stone)
 * Shade Archive+ (3 Serenity Stone, 1 Serenity Crystal)
 * Full Bloom (3 Serenity Stone)
 * Full Bloom+ (3 Serenity Stone, 1 Serenity Crystal)
 * Shock Charm+ (1 Serenity Crystal)

Notes and References
Sérénité