In some situations, for example, when I make my runs in the clan’s accursed tower, when I use shadowsight, the minimap shrinks.
But if, having a small countdown, I manage to cast the skill again before the minimap is back to normal size, the map gets smaller and smaller until everything compresses into one spot.
This doesn’t just happen in accursed towers, but I get the idea that it happens in all “closed” areas, making the skill effectively unusable after 2 or 3 times you cast it.