Another perspective.

As if the end of the world wasn't enough, Sam now had to deal with a murderer and a thief who could infiltrate the most secure section of the base and avoid all security equipment. 

No matter how much they looked there wa no sign of the book and just like that another two days passed. That's when some news finally arrived, sadly they weren't of the good kind.

The scouts sent by the twelfth and thirteenth bases had finally returned. According to them the Resistance headquarters was in a really bad shape. There were more survivors than anticipated, however the number of casualties wasn't small either.

Apparently two Nephilim were responsible for the attack. They were far more powerful than the S class Calamities and the Valkyries were unable to do anything about them.

After wrecking havoc for a while the enemy decided to retreat for some reason leaving a sea of fire and scorched land behind.