Please read the pinned post on creating biomes and dimensions. Please put items for the new Mountains and Nether Updates in their proper categories. Remember portals are structures, that includes Nether portals.
Underworld Dimension? needs info
Unnamed Dimension (with Blazes) needs info
Corruption/ badlands/ dark lands needs info
Wastland biome needs info
Large biomes /Amplified Worlds needs info
Update Magma needs info