http://paste.ee/p/YwEN9
this just randomly started happening, I would give more info but really have none

this issue may be bigger than just your mod. I have had galacticraft bosses spawning in the overworld. something must be screwing with the spawn list... will look into it

Can you try installing this version https://drone.io/github.com/austinv11/PeripheralsPlusPlus/files and let me know if it fixes it?

The latest version of P++ fixes this. And I believe the problem is having too many mobs. If you have further issues, contact other mod devs and tell them that this can be avoided by mods not registering their entity with a global id, they should use this: https://github.com/MinecraftForge/FML/blob/master/src/main/java/net/minecraftforge/fml/common/registry/EntityRegistry.java#L146 instead.