The Armor of the Master is a data simulation of Master Eraqus, found exclusively as a boss in Kingdom Hearts Birth by Sleep Final Mix. As a data simulation, it has a likeness of Master Eraqus and dons his Keyblade Armor as well as uses his Keyblade, the Master Keeper.
The Armor of the Master is a sentient suit of Keyblade Armor that wields Master Eraqus's Keyblade in battle. Its torso is covered of dull, faded green armor and sports a small Mark of Mastery symbol in its center. The rest of the armor on its arms, legs, and chest are predominantly bronze and silver. Its pointed, armored boots are black and gold and its upper arms and thighs have wide, supplementary armor with gold edges covering them.
The Armor of the Master's helmet is silver with a gold chin with jagged "teeth" and a Mark of Mastery symbol of the same color adorning its forehead. The helmet is also decorated by three long, thin, silver pikes on its top and sides. Its hands and neck are covered by a black material.
The Armor of the Master is a powerful user of the Keyblade and Magic. It can perform a powerful melee combo with it's weapon capable of throwing the player into the air and also a high-speed iado-style technique that it follows with Collision Magnet. In terms of magic, the Armor of the Master can fire a rotating wheel of lasers, homing magical orbs and blades and create 5 gigantic homing pillars of fire. It also can fire chains of light capable of allowing the Armor to use unique and much more deadlier version of the player's attacks: with Terra, it can use a series of downward slashes capable of creating earthquakes and use it's light chains to bind him and raise a large chunk of the ground before firing a beam of light. With Aqua, it casts a barrier around itself, performs some spiraling slashes, and unleashes a slow bubble as the finisher, protects himself with a barrier while homing itself at Aqua and creates large, spinning lines of multicolored light that span the field and inflicts status effects on contact. With Ventus, it uses flying slashes capable of launching him to the air, reversal if attacked to counter with a slash from behind and creates two large tornados.
- The music that plays during the battle with the Armor is "Master, Tell Me The Truth", a remix of the Land of Departure battle theme "Future Masters".