So, I was watching Doctor Strange (2016) (cracking film, by the way) and I realised something odd.

The Ancient One says during an early section, before Strange's training properly starts, that believing in an infinite multiverse also means believing in infinite dangers or something close.

Later on in the film we of course meet the Dark Dimension. It's the Dark Dimension - only one, or so it's implied. But surely, in an infinite multiverse, there will be at least one, if not an infinite number of dimensions/universes in which everything is almost exactly the same, with only small differences, for example the sky is a slightly different colour. Something negligible. So why is there only one Dark Dimension? (For that matter the same thing happens with the Mirror Dimension.)