I understand the confusion but there are two halves to the twilight gap, the current crucible training grounds is located near the last city and it was the destination on this fateful day, however the twilight gap referred to here was located on the West Coast of the former United States, it was the evacuation zone that was utilized to charter civilians across the Pacific Ocean to the last city. The legends of the twilight gap have suffered most at the hands of history and the hunters who betrayed the vanguard have all been removed from its retelling. And yes the fallen were the most ferocious of our enemies, they had unified like never before desperate to capture that which guardians hold most precious. However they are only part of why the battle was waged with such intensity. knowing the city of illuminatum which was built over the lost city of angels was in no way as fortified as the last city the darkness attacked with full force hoping to snuff out the light of humanity in one devastating blow. In the end it was the fallen specifically the united house of devils who chased the refugees of illuminatum all the way to the last city's limits and it was here guardians were forced to make their final stand. It is totally within in your rights to doubt me, but I propose that the grimoire released to the guardians of today is abridged heavily censoring and ultimately leaving out whole chapters of our history.