Assassin's Creed's Animus, the virtual reality machine that reads a subject's genetic memory and allows them to relive it as an ancestor, helped the phenomenally successful stab-em-up series to expand beyond the limits of the first game's setting.
That's according to Jade Raymond, the producer of the first Assassin's Creed and now managing director of Ubisoft Toronto, the developer currently making the next Splinter Cell.
"I think that whole layer in the present is really the hub for the franchise, and that's what allows us to continue to expand," she told Gamasutra.
"So that explains why we're in a different period, and it explains why some things aren't consistent, like why are they speaking American English... maybe gamers don't mind so much and they're used to those things, or when you die and you get to retry."
The Assassin's Creed series consists of six games set across various time periods, including the Third Crusade and Renaissance Italy, and stars different protagonists.
But underpinning them all is bartender Desmond Miles, who is captured by megacorporation Abstergo Industries and forced to use the Animus to relive his ancestors' memories.
For Raymond, the inclusion of the Animus played a key role in the success of the franchise.
"But I think the most important part of having the animus and the part in the present is really just because it gave that kind of breadth, and it expanded the universe of the franchise so that it wasn't just a franchise about the Third Crusade when we came out," she said. "You know, there was already the idea that it could expand from the Third Crusade to wherever the present is taking place."
The last Assassin's Creed game, Brotherhood, continued Ezio Auditore's story and returned to the Renaissance Italy setting seen in Assassin's Creed 2. Various time periods and locations are rumoured for the next Assassin's Creed game, including a modern day setting.