The whole point of the loop/bridge time-travel concept proposed here is that there wouldn't be a time where it didn't happen.
From Uriel's perspective, time is not linear. Stand back far enough, and it's apparently wibbly wobbly. By creating a permanent temporal bridge, those 5 times are linked to occur at the same time the first time. There was no time he didn't make the prison.
Picture a piece of string. It's linear, as mortals see time. Now imagine that Merlin got help creating a loop, where two parts of the string overlap, like this:
Where the string overlaps itself is two separate points of time. Now imagine a pin getting pushed through the string, bonding the two points together. That makes them permanently bound together. Only instead of just one loop for two points, there are 4 loops for 5 points of time.
The reason Ms Duck has an issue with it is because messing with time like that would seem to be a very high-level trick. She thinks that it would take a WG-level talent to do it.
But Merlin clearly did it, presumably with help. We can either assume that TWG helped, but if so, why did TWG both involving a mortal at all? Or we can assume that one or multiple lower-tier powers (Mab, Odin, Uriel) worked together to do it.
We know that the Ladies working together were able to channel their attack across multiple times. So the idea that there are time-travel capabilities among the powers isn't outrageous. By nature, Mab should be more powerful than Maeve in that aspect.
Again, the theory breaks down at why do it. There was clearly a major, reality-level need for Merlin to create the DR prison. If it's as difficult as Duck suspects, then it would require a reality-level need for Harry to go back. And I can't think of one.
But if it doesn't take as much power to create a single bridge, and there were a really-really-important-reason for him to go back, then Mab and others might work together to get it done. I still don't know why, though.
Ok I've been away for a while and I just completed my read of this thread. I wish I was in on the conversation from the begining.
With that being said, I feel like some people are having trouble grasping Griffyn's concept of the time loop/ribbon. So here is my swag at it.
Let's back up a dimension. Think in 3 dimensions. Harry climbs up a ladder. He then goes down a spiral slide. Weeeeee! He then walks away from the slide. Think of the ground as a flat plan defined by X-Y space. Think of up as the Z direction. If you are in the sky looking down at Harry, Harry passes through the same X-Y point every loop of the slide. The only difference was in the Z (up) direction. From Harry's point of view he just went down the slide and then continued on his day. From the 2D point of view he passed through the same point.
Now to step it up a notch. To realize that Harry didn't pass through the same 3D point (only a 2D) one you have to observe the 3D path as it happens. Basically you have to be able to percieve time as linear to understand how the trip down the slide works in 3D vs 2D. So now back to the time loop theory. Same basic principle but in more dimensions. Harry is walking through space and time (4D), does something magical to pass through the same point in time he has already passed through. This is only obvious and understandable if viewed from the 5th dimension. So we can only comprehend how he does it while observing in 5D.
I find the Time Travel Loop theory plausable, but unexplainable because I don't think in 5D. How do you explain height to a 2D being?