A Massive Underground Purple Biome in the Overworld

I would love to see a completely new and massive underground purple biome added to the Overworld. Unlike normal caves, this biome should be extremely large and open, making players feel like they are exploring a surface biome rather than being underground. Unique features: - Completely new purple soil. - Unique purple trees, flowers, plants, stones, and blocks. - No naturally generated environmental blocks or plants from existing Overworld biomes. - Unique mobs and creatures. - Special glowing lamps placed at all four corners of every 16x16 block chunk. - Each lamp should provide real light and illuminate an area of approximately 10x10 blocks. - A huge, open environment with a mysterious atmosphere. - The biome should generate underground in the Overworld, not in a separate dimension like the Nether or the End. I want this biome to feel like a completely different world hidden beneath the surface of Minecraft!