The God Blood River was made from the blood of all the gods that had been killed in the Fifth Star Ring. It contained the blood of Godfire Gods, Altar Gods, and even quite a few True Gods. There were even multiple God Lords whose blood ended up in the river!1

Thus, it was no surprise that the river had very intense mutagen levels, as well as an intense aura of death filled with the rage of gods. The banks of the river suppressed all of that with magical barriers. As a result, the mutagen and rancorous energy couldn’t really spread out into the world.0

However... cultivators who entered the water would be infected. If the body and soul were contaminated, then the karma of gods could cause major problems down the line.0

It was only Quasi-Immortal Grand Emperors...0