Juno

Juno, also known as Uni, was a member of the First Civilization and a part of the Capitoline Triad alongside Jupiter and Minerva.

She spoke with two First Civilization descendants; Clay Kaczmarek through the Bleeding Effect, and Desmond Miles in the Santa Maria in Aracoeli, the Colosseum Vault and the Grand Temple.

At one point, Juno also had a husband named Aita, who she was made to euthanize after an experiment by the First Civilization went awry and left him catatonic, during their search for a solution to prevent the First Disaster.

Gathering of knowledge
"Each vault's knowledge was transmitted to a single place. It was our duty – mine, Minerva's, and Juno's – to sort and sample all that was collected."

- Jupiter.

During the rage of the Human-First Civilization War, Juno was among those who avoided the fighting. Along with Jupiter and Minerva, she built several temples underground, safe from the war, in which to research methods of salvation from the impending catastrophe. The findings of each vault were sent to a single location, the Grand Temple.

Juno remained in the Grand Temple with Jupiter and Minerva to sort through the possible solutions and test those that they found encouraging. They evaluated six in succession, finding each progressively more promising, however, their efforts came too late. Before any solution could be implemented, the catastrophe struck, killing nearly all of the First Civilization and humankind.

Enlisting aid
"Thousands of years this message waited. Soon its promise shall be fulfilled. Go forth, with eyes open to all but the truth."

- Juno speaking with Clay.

After experiencing long sessions in the Animus, Clay Kaczmarek began suffering from the Bleeding effect, and became confused with the division of his genetic memories from his actual ones as a result.

Around this time, Juno approached him, introducing herself and telling Clay she had "come to show [him] the way." Some time after, Clay claimed to be able to see "what has been, what will be."

Juno acknowledged him, saying that what he needed to do was clear, and that he should help Desmond Miles. In response, Clay blatantly refused, but Juno only said that her message had waited thousands of years and that its promise would be fulfilled. When Clay's eyes were opened to the truth of Lucy Stillman's allegiance to the Templars, he consented to Juno's request, and went on to aid Desmond while he was trapped in the Black Room.

Balancing the scales
"A hundred years I might speak and still you would not know us. You with five senses. Us with six. The one we kept from you. To be safe. Now, you can never know. Only try."

- Juno to Desmond.

Juno appeared four times as a holographic form to Desmond Miles, a modern day Assassin, as he passed through the Santa Maria in Aracoeli, in search of the vault hidden within it. However, none of the others who had accompanied Desmond were aware of her presence.

Juno spoke to him of the vaults and her people, before elaborating on the warning Minerva had previously relayed to Ezio Auditore da Firenze in 1499; though her tone was noticeably more hostile towards humanity. Calling man ignorant, Juno spoke of the blending of the bloodlines between human and First Civilization – a line from which Desmond descended – and angrily regretted that they should have left man as they were.

When Desmond, Lucy Stillman, Shaun Hastings, and Rebecca Crane reached the Apple of Eden within the vault, Juno spoke to Desmond one final time. Saying that the "final journey" had commenced, she told him of a woman who would accompany him, but first, the path needed to be opened and the scales balanced. With that, Juno forcefully took control of Desmond, and forced him to kill Lucy with his Hidden Blade.

The Grand Temple
After Desmond recovered from the coma induced by Juno's actions, he along with Rebecca, Shaun and his father William Miles, arrived at the Grand Temple. Upon approaching the inner parts of the building, Juno's voice reached out to Desmond, urging him to find the key and also triggering the bleeding effect. Because of this, Desmond was forced back into the Animus to find the location of such a key through the memories of his ancestor, Ratonhnhaké:ton.

In his breaks from the Animus, Desmond explored the Temple and came face to face with Juno multiple times. In each meeting, she detailed the six ways in which the First Civilization tried to stop the impending doomsday, including using the Pieces of Eden to will the threat away and transferring themselves to new bodies for protection. The latter revealed that Juno once had a husband by the name of Aita who she was forced to kill after the transfer into the machine-like bodies malfunctioned. By checking his e-mails, Desmond also received numerous messages from Juno, expressing her anxiety over finding the key and urging him to hurry.

After finally uncovering the location of the key, the Assassins were able to enter the inner chambers of the Temple. It was here that Juno appeared again, urging Desmond to use a pedestal-like device with his touch in order to protect the world from the solar flares. However, Minerva also appeared in this chamber and revealed Juno's true intentions. In the past, she had tried to use the First Civilization's technology in order to conquer the world for her own gain, rather than save it. She was sealed inside the Grand Temple by both Minerva and Jupiter for her crimes, but she managed to survive. If Desmond was to activate the pedestal, them Juno would be freed to try and do the same again. Juno tried to reason with Desmond about the fate of the world, urging him to use the device lest history repeat itself again. He ultimately agreed despite pleading from Minerva, for the good of the planet. Whilst the other Assassins escaped, Desmond touched the pedestal and was killed by the device as Earth was saved, suffering minor solar flares and its effects. Now freed from her prison, Juno thanked Desmond for playing his part before stating that it was now time she played hers.

Trivia

 * Juno was a Roman goddess, Queen of the Gods, protector, and special counselor of the state. She was equaled with the Greek goddess in both characteristics and personality.
 * Juno's other name, "Uni", was the Etruscan equivalent of Hera.
 * Juno was not actually named during Assassin's Creed: Brotherhood, nor did her name appear during the end credits. Rather, Juno's name was revealed by Nadia Verrucci on her website.
 * Lucy's password on the Hephaestus Email Network was "Juno57," as revealed in an e-mail that Desmond received from Erudito in Assassin's Creed: Brotherhood.
 * In the Assassin's Creed: Revelations novel, it was stated that Ezio encountered Juno, though exactly when was unspecified.
 * When contacting Desmond through e-mail in the Grand Temple, Juno initially finds it difficult to send through legible messages. Her name as the sender is a string of binary code.