[quote=@rush99999]
<Snipped quote by ShiroKiyoshi>

What biome do the purple areas of the map represent?
[/quote]

The spread of demonic miasma. The monsters you see here are extremely mutated and way more dangerous than anything you're normally used to. in addition it does not actually represent the influence of the demon horde on the world it's just the influence of the miasma that comes with them that is distorting the world around you.