Can someone explain the end of Assassins Creed II

Ezio defeats Borgia (then, Pope Alexander XVI) and journeys into the hidden chamber where the preserved essence of Minerva, the last remnant of a humanoid race of godlike beings, greets him. However, she is able to see the future and knows that Desmond Miles is reliving Ezio's memories. With this knowledge, she explains that the world, and all of its inhabitants, were destroyed by a mysterious cataclysm. She warns Desmond that this disaster will occur again unless he takes proper action, and then fades out of existence, her purpose having been fulfilled. Ezio, unaware of what has transpired, simply asks,
"Who is Desmond?"

Meanwhile, Desmond himself leaves the Animus with Lucy and the other Assassins, fully-trained and ready to combat the Templars that have invaded the compound. The Assassins and Desmond escape to a cabin in the forest, knowing now that the "war" being waged must be ended, or all life on Earth will die.