Biome Bundle is a world pack for Open Terrain Generator which must be downloaded separately here.
It is a completely custom world generator containing a huge pack of over 400 original biomes with over 2000 structures including custom trees, rocks, caves, dungeons, villages and much more.
The content consists of 4 main parts:
Custom biomes and terrain
Custom objects (trees, rocks, etc)
Custom structures (Dungeons, ruins, etc)
Custom mob spawn rules (in select biomes)