The Underrealm

Have you ever been mining down and hit bedrock and wondered what was under it? I have came up with the idea that if you have a netherite pickaxe and mine the bedrock, you will reach the Underrealm. This is a biome that is covered in glowing fungi and coral above water and houses many ecosystems with rare mobs. Each area is different and themed after an element of earth. Fire, water, air, ice, earth, plants, lightning, sand, metal, insects, rainbows, myths, darkness, light, crystals, and more. Each land houses a boss that when killed drops a gemstone that matches that area. When all the gemstones are placed in a giant ring around an arena battlefield, the ultimate boss will awaken and attack you. This boss will be stronger than the warden. If you kill the boss, you will earn the strongest set of indestructible tools and armor that is fully enchanted. Each area has their own mobs, blocks, ores, and plant life. This could be a great theme for the 1.21 update or any future update.