The Great Spirit War

The Great Spirit War (森羅変転 or ワールド・フラクション) is the war when the Angel Massacre took place.
It started when a spirit called Mëădeős went psycho and tricked the races into killing the Angels. The Angels were unprepared and after Mëădeős was found out most of the Angels were already dead.
The Second incident was when the leader of the Human race decided to kill the remaining Angels to stop them from taking revenge, this happened 5 years after the first incident.
The outcome ended with half of the humans being killed and a single city of the Angels remaining; Angelios (冒険者たちの定住化). After another five years the humans developed a single weapon the could destroy the city. They launched it in secret and it hit the Angeosphere directly and resulted in all but three Angels being murdered. They Angels had been creating a machine of magic that was launched just as the weapon hit Angelios and with it all knowledge the angels had. Later on using this knowledge the Remaining angels summoned the 'perfect' angel, marking the end of the War.
In total over 100,000 Angels were massacred giving this war the nickname of the Angel Massacre and although this is the main point of The Great Spirit War, this wasn't all that had happened. The reason it was called The Great Spirit War was because many people of the races had tried to reach the spirits to try and steal their powers. This had Enraged Khaos and he had send out spirits to go to war with the people and in the end the races surrendered and so it was named the Great Success of the Spirits and was later named The Great Spirit War.