So what's in an evil biome?

I'm curious about evil biomes. What makes a biome evil? How does being in an evil biome change the game?

 

It's a place where politicians raise the dead for direct action campaigns.

 

Clockwork Romneys. And Canadian climate obviously.
And steam-driven ponycorns. Because a ponycorn is much more evil than a simple unicorn!

 

Everything looks like John Malkovich

 

Evil biomes have Oreo shrubs, but no cows to milk.

 

It starts with evil earthworms. Evil earthworms eat dirt, and then poop evil dirt. Once a sufficient amount of the dirt becomes evil, the plants that grow in it become evil. The animals that feed on the plants don't seem particularly evil, but their offspring quite clearly are. When predators eat the evil offspring, no noticeable change -- but once again, their children are born red-eyed, oozing some indefinable substance, and prone to making soul-shattering pronouncements in dead languages.

Where do the evil earthworms come from?

Aunty Strychnine's Befouled Bait Shop, of course. After all, how are you supposed to catch the Maalwhaal without evil earthworms?

 

You can tell you are in an evil biome when you see larva fields around you.

 

A refusal to use the Metric System. Plain and simple.