The image of Minerva appears in Assassin's Creed II when Ezio Auditore discovers it in the vault underneath the Vatican, which Ezio accessed using the Staff and Apple. Although she refers to herself as Minerva, she has had many names, playing the part of many female gods throughout mankind's history, the given examples being Merva and Mera. She died some time before the message left for Desmond (through Ezio) was created, and given the holographic nature of the encounter, her likeness (or possibly even consciousness) must be being projected by some ancient computer system. She claims that others of her kind are present, held within sorts of columns covered with inscriptions, she mentions Juno, who was before called Uni, and Jupiter, who was before called TInia.
Her race though are not in fact gods, but a human-like people much more technologically advanced than us, who watched over humans when we were merely a fledgling species which in fact they had created to be subservient to them, using the pieces of eden to design and retain dominion over us. But humans grew unruly and rose up in war against 'They Who Came Before', using our numbers against their power. During the trying war, all eyes were focused on 'earthly concerns' i.e. the war, and their species did not notice a surge in solar activity, and (given what is shown in the cutscene) some kind of flare from the sun erased most of both our populations, baking the earth. We rebuilt together, but slowly her kind died out. Her exact words were 'We are gone now from this world. All of us. We can do no more'. She also makes it clear that the only reason we survived, and that they now wish to warn and help us, is that we were made in their own image. Since then their relics have been misunderstood, forming false religions instigated by people wielding the powers of the pieces of eden, pretending to be gods. She suggests that Desmond seeks out the 'other temples' where information on how to stop the same near-extinction by solar activity happening again can be found, the residences of other (we assume projections) like her. She tells Desmond that he must hurry, as time is short.
In the scene in which she divulges this, she is not talking to Ezio, but Desmond. Somehow, the message knew that Desmond would be replaying Ezio's memories in the future, and so she looks not at Ezio but directly at the camera when she speaks, apart from when she is telling Ezio that this is because he is merely a prophet, carrying her words through his memories until Desmond can later view them and get the message.
Minerva is voiced by Margaret Easley.