getting this with the latest version and the latest build of Spigot http://hastebin.com/ilihikuyig.avrasm

looking at the error more it seems to have something to do with Terrain Control and a custom Biome that I've made.

Sounds like it: https://hub.spigotmc.org/javadocs/spigot/org/bukkit/block/Biome.html

I'll see if I can attempt to make EHM ignore custom biomes though.

Hmm... not sure if this is possible, since it's just flat out throwing an exception if it can't return the biome in the Spigot API... so not sure how I'll go about this at the moment - I wonder if there's other ways to get the biome name without having to do getBiome(). https://github.com/MLG-Fortress/ExtraHardMode/blob/master/src/main/java/com/extrahardmode/features/Tutorial.java#L266

I know next to nothing about coding so I'm just tossing this out there but does Terrain Control have an API where you could poll it for the custom biomes instead?

That'd require me adding it as a dependency, which I wouldn't want to do nor should do anyways since those biomes are entirely custom.

I think the easiest way (and probably the proper way) to fix this is to just use a try-catch statement.

The error doesn't seem to be damaging to the game play itself, everything still seems to work. Is there a way to just suppress the error?

That was my intent, and a try-catch block should do that.

Please try 3.7.2, and comment here if you're still having issues.

If you don't know how to reproduce, try placing a dirt block in your custom biome. Make sure you're in a mode where ExtraHardMode applies to you (i.e. not op, and in survival mode).