Crimson and Corruption [1.3]
In the newest release I figured out how to add shadow orbs along with alters!
I edited this world with TEdit so that there is 2 crimson biomes and 1 corruption biome on the far right of the world. The original biome was a crimson biome so it will be almost the same! To install just extract the file into your world saves folder.
World Size: Large