Godfall

The Downfall of all Pantheons and destruction of their homes, leading to a cataclysm affecting the material plane as well and near extinction of all life on the planet.

DC10 History/Religion/Arcana: check for common knowledge

Occurring over the course of a single year, the event rippled through every single pantheon and realm. Several gods outright disappeared and many more were cast out of their homes to join the world below, no longer able to express miracles as previously done. The realms themselves suffered major scarring with the majority being damaged and large portions ending up on the planet during the shattering. Holes that were left allowed the very essence of magic and astral void to seep in and turn the remaining portions to hostile landscapes. It is during this time that nearly every civilization and all life in the material plane was wiped out in a single year. Sentient races barely survived and have been able to slowly rebuild civilization. 

Every known godly realm was wracked by this event with several being sundered into several pieces. Large portions of these realms/planes have been merged  into the Material Plane as result which caused untold damage to the surrounding areas they appeared. This resulted in voids appearing where these portions disappeared from, causing raw festering wounds to all reality. Scientific and religious entities have failed in explaining how this event even happened and the resulting passage of time has made all but impossible to be uncovered.