Overview
Protect important builds without attempting an impossible early full-world cleanse.
How it works
Corruption, Crimson and Hallow can spread through convertible blocks; Hardmode accelerates or changes relevant processes.
How to use it
Protect important towns, Jungle infrastructure and farming areas first, then target larger cleanup.
Mistakes to avoid
Do not dig randomly and assume any gap blocks all spread mechanisms.
World Evil Containment Plan: detailed guide
Inspect the world before Hardmode
Locate obvious Corruption or Crimson fronts and mark the towns or Jungle you need to preserve. Decide what really needs protection. Cleaning the entire world before Wall of Flesh is usually a poor use of resources relative to early equipment and routes.
Contain high-value areas
Design separation trenches with correct spacing and block treatment appropriate to your version; address thorns and other propagation routes. Move NPCs if a site becomes compromised. Review nearby underground conversion instead of looking only at the surface color.
Use Hardmode tools responsibly
The Steampunker sells biome conversion equipment after mechanical boss progression. Carry the correct solution and test a small area first. Avoid damaging useful farms or creating unwanted biome switches inside your base. Some materials and farming strategies depend on retaining enemy biomes.
Monitor rather than panic
Recheck key passages after defeating major bosses and when underground routes seem different. Use the Dryad for world status and maintain travel paths. A playable world does not need to reach absolute purity; focus on preserving functionality and access.