Deeper Dark/Darker Dephts Dimension

The dimension would be accessed trough the portal in ancient cities. In the overworld there is bedrock at the bottom but not at the top, in the nether there is bedrock at the blttom and at the top, in the end there isn't bedrock, so in this dimension bedrock could be at the top but not at the bottom. The deeper you go, the harder it gets. Maybe you wouldn't even loose your items if you die there but you would loose the items obtained from this dimension. So you could make it a really hard dimension. There could be cube shaped labyrinths with treasures in the middle or mobs that only move when you look away. At the top of this dimension there would be caves, but as you go deeper, you get closer and closer to the void and the caves transition to floating islands before the void comes. Elytras may not work in this dimension.