Place in the books
Dark Island is one of the most psychologically memorable places in the Chronicles. Lewis does not need a long stop there to make it work. The idea is strong enough on its own: a place where nightmares become real. That gives the voyage one of its sharpest turns from wonder into dread.
The island matters partly because it is so brief. Readers do not get to master it. The ship escapes it. That makes the place feel less like a territory to understand and more like an encounter with raw terror at the edge of the known world.
Why the location matters
Dark Island shows that the eastern voyage is not a simple ascent into beauty. Fear travels east too. The farther the company goes, the more exposed they become, and Dark Island is one of the clearest expressions of that truth.