This emerald is used to get Hyper Pot Platinum. 1st you need Reborn arrow then DIO's diary and the hyper chaos emerald.
the spawn rate is 45 minutes with 1/10 chance
HOW TO GET:
you need to get shadow pot platinum
It can also spawn around the map, but the spawnrate isnt yet confirmed. all that's known is that it spawns under an hour, since i found it most frequently then.