The War in Heaven was a major conflict, that should decide the fate of Aard.
History
Disturbed by attempts of the Aardians to breach the plane of the gods and thus gaining access to their divine powers, the gods became restless. Reminded by prior events with their past creations some gods voiced concerns and wanted to destroy all life and start anew.
A debate would start and ultimately split the gods into two groups, those that opposed the destruction (Preservation) and those for it (Ruination). This debate would become heated and soon gods would fight against each other.
While the Gods of Preservation tried to keep the Gods of Ruination within their plane, they soon slipped out through the crack that has formed. In a twisted scheme, they started to corrupt the minds of Aardians in order to chase them into their own destruction - having witnessed their wars prior.
The Gods of Preservation in turn descended as well to Aard and raised their own armies, to oppose their own brethren. Both sides started to arm their proxies with weapons, artefacts and some of their divine powers, in the hopes to bring the conflict to a quick end.
Only the Aardians themselves were able to stop the madness, by using all their gained powers and knowledge to banish the gods, ultimately bringing destruction in the form of the Rupture.
Aftermath
Banished back to their own plane, it is believed the gods still fight. A magical seal covering the crack the only defence against the return of Ruination. But the seal isn’t perfect and the gods still convey some influence over the inhabitants.