It is a spinoff and prequel to their popular game Rifts, which uses a similar form of Palladium's Megaversal system.

In the early 2000s, Palladium was experiencing decreasing sales, so the company continued to produce new settings in an attempt to offset this.

[1] How it was originally intended: A parallel dimension to Rifts where the massive deaths were caused a minute after midnight when the released Potential Psychic Energy (P.P.E.)

The way it is now: The Chaos Earth setting is the period in Rifts history where the deaths caused by a limited nuclear exchange happened at midnight, in proximity to the winter solstice, in conjunction with a celestial alignment; which magnified the PPE released from the deaths sending all the ley lines into overdrive.

Nexus, formed where leylines cross surge creating Rifts, large tears in the fabric of reality.