Arda Nova is a large sized Aragami that serves as the final boss of God Eater.
Prior to God Eater Resurrection it was comprised of two separate Aragami, a Large sized God and a Medium sized Goddess. In said game, however, the God part of the Arda Nova became a breakable "part" of the Aragami as a whole.
The following information is taken from the offical in-game descriptions of the Aragami found in the NORN Terminal's database.
God Eater Burst
A gigantic human-form Aragami built by Director Schicksal under utmost secrecy. The technology for controlling the bias factor was adapted from God Arcs, and so it's a kind of human-form God Arc.
The Arda Nova can only suffer damage when it is actively attacking, and it is comprised of two bodies, one a goddess, the other a god. Should you defeat the god first, your close-range attacks on the goddess will be more effective as the god isn't in the way.
God Eater Resurrection
A gigantic human-form Aragami built by Director Schicksal under utmost secrecy. The technology for controlling the Bias Factor was adapted from God Arcs, resulting in its moniker, the "Human God Arc." It is compromised of two bodies, one a goddess, the other a god.
ATK Element : Divine
Weaknesses : Blaze, Freeze, Spark, Divine
Based off of the Hindu deity Ardhanari, that symbolizes the root of all creation.
Once the female body is defeated, the male will also fall, but the female can act independently if the male is defeated. Defeating the God body yields additional bonus rewards not gained if the Goddess is destroyed first.
While enraged, the voice of Arda Nova will become male (Johannes) instead of female.
Regardless whether the Goddess or God part is defeated first, In God Eater Burst both bodies can be salvaged for materials.
In God Eater 2, Arda Nova and Fallen Arda Nova do not appear in any Story or Free missions, due to having already been destroyed in the first game. Tsukuyomi, however, does appear in missions.
It can be noted that the face of Arda Nova's male body closely resembles Fenrir's logo of a wolf's face, which emphasizes the reference to Loki's wolf son from Norse mythology whose role in the Armageddon-causing battle royal of the Norse gods, formally known as Ragnarok, was to devour the king of Asgard, Odin, only to be in turn killed in battle by the hand of Odin's son, Víðarr (anglicized Vidar).
In God Eater Resurrection, the God is no longer considered a separate entity and is instead merely a breakable part of the main body. Breaking the God portion will NOT put it out of commission.
On that same note, only Helios-prefixed materials drop from unbounding parts and devouring.
The Arda Nova's defenses are normalized in God Eater Resurrection; it can suffer normal damage even when not attacking.