Board Thread:LotR Mod Technical Support/@comment-27387657-20151231164048/@comment-25101089-20160101185834

From what I can tell, this is the cause of your crash:

Now, unfortunately, this is not something I can fix, because to do so I'd have to edit Forge's code, and I can't. It's not something the other mod can fix for the same reason - though they could somehow prevent their mod from generating in Middle-earth, but that would not be straightforward.
 * The Middle-earth world is generating.
 * The mod "draco18s" tries to generate something called "PlaceTraps".
 * This generation depends on biome, so it gets the current biome, and looks for its properties in the Forge biome dictionary.
 * Unfortunately, the Middle earth biomes use a separate biome list from Overworld/vanilla/other mod biomes. This means that the Forge biome dictionary tries to find a normal biome matching a Middle-earth biome's biome ID.
 * But since there is no such biome, the code is given an object that doesn't exist ("null") and is trying to access its properties. Obviously this is not possible, so an error has occurred.

It's not even something Forge can fix, because their code is built on a very reasonable assumption - that all biomes existing in the game will belong to the normal 'biome list'. I can't imagine anyone would have ever predicted that a mod would try to create its own separate biome list and have it work successfully, and to be honest the developers would probably try to tell me off for doing so.