Sudden Siege of the Silver City

The Sudden Siege of the Silver City was a short-lived attack on the High Heavens by demons from the Burning Hells, and was the first such attack on heavenly property the Pantheon had witnessed. It is the battle accredited with starting the Eternal Conflict between Heaven and Hell. The event damaged Meinolf's reputation but boosted Irmhild (AoC Universe)Irmhild's.

Result
The siege was successfully defended by the Aesir, but it proved that there was an evil force lurking in the Great Unknown waiting for them, and vindicated Irmhild, who had previously called for a defence force to be created in the event that Heaven were ever attacked.

Without the Aesir and Vanir's intervention, the Silver City would have been terribly damaged. Instead, it wasn't even broken into; only the Eastern Gate suffered from the attack.