The Great Celestial war was from a game, Obey Me, and was well a long story.
An angel named Lillith went down to the human world a lot and soon dud fall in love with a man. Then after a very long time the man got sick and was about to die, then she took some food from the Celestial Relm and gave it to the man, to expand his lifespan.
She soon got in trouble for it and was going to be sent to death but Lucifer and his brothers saved her and thats how it started.
That was stupid but hope it helps.
Lillith almost died during the Great Celestial War.