This tropy is called Master Defender. You need to get all of Goofy's weapons
Knight's Shield (Default Shield)
Stout Shield (250 munny)
Genji Shield (Defeat Yuffie in Hades Cup)
Mythirl Shield (750 munny)
Golem Shield (1000 munny)
Defender (Dropped by Defender)
Onyx Shield (2800 munny)
Smasher (250 munny)
Gigas Fist (1000 munny)
Adamant Shield (4000 munny)
Herc's Shield (Defeat Hercules in Hercules Cup)
Dream Shield (Speak to Merlin after acquiring all spell arts)
Save the King (Win Hades Cup Time Trial)
Mighty Shield (Chest in World Terminus at the End of the World)
Seven Elements (Synthesize)
Dream Shield
For the Dream Shield you must collect Spell Arts from White Mushrooms throughout the game, they will give you a spell art after you use the same spell on them three times. The easiest way to do this is to simply wait in front of one and wait for them to go into the pose you want for your desired spell. Here are the poses the white mushrooms do and the proper spells to use against it:
Shivers - Fire
Fans itself - Blizzard
Light appears overhead - Thunder
Falls to ground - Cure
Spins - Aero
Stops - Stop
Floats - Gravity
Once you have acquired them speak with Merlin for your Shield. If you need quick locations for White Mushrooms here are spawn points they will likely show up in:
Deep Jungle: Camp
Halloween Town: Graveyard
End of the World: Linked Worlds
Atlantica: Sunken Ship
Agrabah: Treasure Room
Wonderland: Lotus Forest
Seven Elements
This will be in the last recipe list during Item Synthesize, the materials needed for this are:
3x Blazing Stone
3x Frost Stone
3x Thunder Stone
5x Dazzling Stone