Zero Reverse

The Zero Reverse Effect was caused by an intentional overloading to the Enerdy system. The result of this lead to an negative energy of which was send down into the Earth, in the form of a massive amount of dark energy. The first Enerdy system developed 17 years prior to the pilot of Yu-Gi-Oh! 5D's had this occurence and resulted in a disastrous tectonic shift that split Domino City into two. Thus a channel into the underworld where the Earthbound Immortal's were sealed was opened as well, allowing them to spread their influence over those chosen by these Gods themselves.

Background
It was revealed that the lead developers within the Kaiba Corporation M.I.D.S, were Yusei Fudo's parents and that they both lost their lives during the catastrophic incident. The leader of the Dark Signers, Rudger was involved in the project, along with his brother Rex Goodwin, both being assistants at the time. Later on Rudger tells Yusei and the others, that the Professor (Yusei's father) wanted to cancel the Enerdy research, as at that time the system itself was quite unstable. Furthemore he got to the conclusion that there might be an accident, however his request to cancel the project was completely rejected by its sponsor.

With the professor being uncooperative, the research ended up being handed to Rudger as the new head developer. This all ultimately led to the occurence of the incident, as Rudger himself 17 years ago was one of the choosen Signers. Unfortunately he had decided to go into the path of darkness, so then chose to become instead a Dark Signer. So in order to be reborn as one, Rudger killed himself by overloading the system which ultimately lead to the disaster.

The incident also the reason behind why Domino City was detached and splitten into what is known as New Domino City and Satellite, with Satellite being the area hit hardest by the energy release. The public was told that the events were caused solely by a natural disaster (this being the cover up story). One of the leaders of the Momentum Investigation and Development Section M.I.D.S (the group that created the Enerdy system), survived the accident and took over the Public Security Bureau, and created the massive cover up story, taking all possible measures to ensure no one would accidentally see through it and learn what really happened.