The Archive was an interdimensional library in the far future. It contained books from all known universes. Some even speculated that the Archive contained the multiverse and not the other way around. (AUDIO: The Archive)
The Archive resisted Abby and Zara's attempt to change history. (AUDIO: The Battle)
The sisters later found a copy of Kronos Vad's History of Earth Volume 36,379 in the Archive but from a universe alternate to their own. It described an invasion of Earth by the Gomagog. They took it to Earth in the past as a warning, with the hope that it could prevent the invasion from happening in their own universe. (AUDIO: The Archive, Kronos Vad's History of Earth (Vol. 36,379)) Later, Vienna Salvatori and Bernice Summerfield took the book to the Archive for safekeeping at a point in time before Abby and Zara found it, making its existence a bootstrap paradox. (AUDIO: The Phantom Wreck)
Abby and Zara later came back to look for a cure for Wing. (AUDIO: Consequences)