This is the further evolved form of Imperial Knight Aegis Gundam, who overcame the trials of the Three Gates of the Underworld. His combat capabilities have expanded through cooperation with the Lifter. He has restored the power of the Mythical Beast to the King Shield, which had lost its power and been shattered by the Black Knight Banshee.

The Lifter is a remote flight unit that Justice controls freely with his magical power. It can fly alone or carry Justice Gundam.

Justice Gundam confronts the resurrected Emperor of Darkness, Sieg Zeon. At that moment, a great power wells up from within him, creating a miracle.

In the battle in the Underworld, Justice Gundam grew not only physically but also mentally.