This terraria world is an entire mushroom biome, only the corruption biome is still there (obviously, how else do you beat the Eater of worlds)
preview: https://youtu.be/F_C4Ex_3CtY
Warning: this world's template was the not the bees world, you may see queen bee larvas everywhere
Last tested: 29/12/2021 - Terraria1.4.3.2