In N Terraria there are two New options for created worlds, "World difficulty" & "Biome option".
In World Difficulty section there are three sub settings that change Modifiers.
Normal difficulty Adds the least modifiers and spawns
Champion difficulty Adds more modifiers and spawns
Suicide difficulty Adds the most modifiers and spawns
In biome option section there are two sub settings.
Bloody world By applying this setting on the world it lets the The crimson biome spawn.
Evil world By applying this setting on the world it let's The Corruption biome spawn.