I tried both layouts, with and without CC - same results. 0.4 works without issue. I remeber that in the past Emoniph added some compatibility on his side in case of ATG.

java.lang.RuntimeException
at rtg.world.biome.WorldChunkManagerRTG.(WorldChunkManagerRTG.java:50)
at rtg.world.WorldTypeRTG.getChunkManager(WorldTypeRTG.java:27)
at net.minecraft.world.WorldProvider.func_76572_b(WorldProvider.java:61)
at com.emoniph.witchery.dimension.WorldProviderDreamWorld.func_76572_b(WorldProviderDreamWorld.java:75)
at net.minecraft.world.WorldProvider.func_76558_a(WorldProvider.java:44)
at net.minecraft.world.World.(World.java:244)
at net.minecraft.world.WorldServer.(WorldServer.java:97)
at net.minecraft.world.WorldServerMulti.(WorldServerMulti.java:14)
at net.minecraft.server.integrated.IntegratedServer.func_71247_a(IntegratedServer.java:65)
at net.minecraft.server.integrated.IntegratedServer.func_71197_b(IntegratedServer.java:92)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:387)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)

That's weird I use witchery in my default test environment and never had a witchery crash. Can you dump the whole fml latest log plz

Sure http://pastebin.com/X0ExkCRR .

Looks like #382 is a duplicate -- same error, different biome-adding mods.

Fixed in aea3b24

That was a deliberate crash I put in because I was expecting problems with non-Overworld dimensions. Witchery is trying to create the Dream dimension with the RTG chunk manager - will that work?