What lies at the end of Chaos? It is Nothingness!
Crossing the darkness more ancient than Chaos, Jiang Chen arrived at the end of the River of Space-Time, which is also the end of Chaos, a world of void.
This is true Nothingness, where nothing exists, not even the concept of Nothingness.
The River of Space-Time churned, raising terrifying giant waves, engulfing Jiang Chen, attempting to send him into this void.
This is the means by which Time and Space seek to utterly kill Jiang Chen, sending him to the end of Chaos, that world of Nothingness, and then letting the original void devour him.
Nothingness is the beginning of Reincarnation, as well as its end, possessing the power to turn all things into void. As long as one has not reached the Eternal Realm, upon arriving here, they will return to Nothingness, and nothing will exist.
And if one is devoured by Nothingness, they are truly dead, unable to ever be resurrected.