A shield once held by a great hero.
Final Fantasy description
Master Shield is the strongest shield, available only in the Advance and later versions. It provides 19 Defense, 31 Magic Defense, +1 Agility, +1 Intelligence, and resists all elements and statuses. It can only be equipped by the Warrior, Knight, Red Mage, and Red Wizard classes. It can be found in the Labyrinth of Time by defeating Chronodia while it's just in Kraken mode.
Master Shield is a shield that provides 8 DEF and Shield skill +10. It can be equipped by level 52 Warrior, White Mage, Red Mage, Thief, Paladin, Beastmaster, and Samurai. It is dropped from Southern Shadow.