2. A Malfunctioning Animus
I've always had this fascination with the idea of the Animus malfunctioning while Desmond was using it, causing all sorts of craziness to occur such as 'Ancestral Memory Bleeds' - the idea that, through the Animus's error, players are forcibly switched between controlling Connor, but in AC I's world; then suddenly Ezio in AC III's; cut to Altair in Renaissance Italy, and so on. Of course, for dramatic effect, Desmond would also be powerless to exit the Animus, as a convenient by-product of the malfunction. Finally, there could be a compression of time in which Desmond finds himself trapped in a world stitched together from the settings in all three AC games and must find a way to right the Animus's malfunction before it quite literally fries his brain. How does he achieve this? Well, my idea is thus: he, with the help of the ever-present team, deduce that there's only one way to fix the Animus from the inside and that's to travel beyond the limits of the memory (you know, that polygonal wall that blocks you from traveling too far in any one direction - which is somewhere that I, for some reason, have always wanted to go. In all honesty though, I'd question the possibility of something like this; with the two separate game engines that are now both a part of the Assassin's Creed Franchise with the release of III, it sounds like a logistical nightmare and probably too expensive to justify its creation as a simple DLC package. Still, I'd certainly pay to play it.