Master Defender
To obtain master defender, you must acquire each of the following shields for Goofy.
Knight's Shield - Default
Stout Shield - Item Shop - 250 munny
Smasher - Item Shop - 250 munny.
Mythril Shield - Item Shop - 750 munny.
Gigas Fist - Item Shop - 1000 munny.
Golem Shield - Item Shop - 1000 munny.
Onyx Shield - Item Shop - 2800 munny
Adamant Shield - Item Shop - 4000 munny.
Genji Shield - Defeat Yuffie in the Hades Cup.
Herc's Shield - Complete the Hercules Cup.
Save the King - Complete the Hades Cup time trial.
Defender - Random Drop - Dropped by Defender (0.2%).
Mighty Shield - Chest at the World Terminus.
Seven Elements - Item Synthesis.
Dream Shield - Speak to Merlin after acquiring all seven spell Arts.
Mighty Shield
Here's where you can find Goofy's Mighty Shield that will help you towards your goal of unlocking Master Defender. The location you can find it is called End of the World. Specifically, the chest is located in the Neverland zone.
The following video guide shows the step-by-step process.
Video Tutorial
Dream Shield
This one might take the longest to farm. You have to win the white mushroom mini-game for each magic element and return them to merlin.
Video Tutorial
Defender Shield
Defender shields have an extremely low chance of dropping from slain Defender Heartless found in Hollow Bastion and other locations. The quickest areas to farm this are in Traverse Town in the Hotel Hall and District 3. I dropped mine in District 3 after about 500 slain Defenders. It will help your chances if you equip
Lucky Strike and
Encounter Plus abilities