PSA: Please report this mod on CurseForge as it's a fake mod claiming to be Lithium but instead spawns Withers with some frankly rude names. : r/feedthebeast
How to properly use and install the Lithium mod for Minecraft
Edit your world from within Minecraft with Advanced Creation. It's RTS-like perspective lets you easily edit large areas. You can get it on CurseForge: https://www.curseforge.com/minecraft/mc-mods/advanced-creation : r/feedthebeast