Here is a single player map where we can go to 8 worlds. And in each of them you will need to find 8 emeralds. Note that this map is not easy, you will need to try hard to pass it.
How to install The 8 Portals
- Download and install Minecraft Forge
- Download map
- Unzip it and copy to C:\Users\User_Name\AppData\Roaming\.minecraft\saves