The Axiom, or The Great Reason (大いなる理), is the binding force of the universe, from which everything originates, and will eventually return to. Existing beyond time, space and the infinite cycle of transmigration, it is a fully unknowable entity, and the true Supreme Being of the Megami Tensei Series.
Though YHVH, the God of the Covenant, believes to be the One True God, he is in truth only a rogue avatar / aspect of The Axiom, the truth source of existence. By creating the physical multiverse, yet simultaneously remaining outside of it, and debasing all other deities as false, YHVH established himself as almighty and supreme. However, he was not behind humanity's creation. Instead, humans were formed by The Axiom itself, and with the Power of Observation bestowed upon them, they would be able to shape their own destiny, through their own beliefs and thoughts.
Though The Axiom rarely interacts with the created world, it will sometimes act on behalf of humanity. On times of great suffering and despair, it will create a Messiah, a human of great power who's Observation can create a path for all mankind.
Powers and Stats
Tier: Unknown, likely High 1-C
Name: The Axiom, The Great Reason, The Great Will
Origin: Shin Megami Tensei
Classification: Supreme Being, God, Abstract Entity, Binding Force of Reality
Attack Potency: Unknown, likely High Complex Multiverse level (Infinitely superior and transcended to anything else in the Shin Megami Tensei series. Even the true form of YHVH is only an infinitesimally-small fragment of it.)
Lifting Strength: Immeasurable
Striking Strength: Immeasurable
Durability: Unknown, likely High Complex Multiverse level
Range: High Complex Multiversal
Standard Equipment: Inapplicable
Weaknesses: None Notable