The Night Mountain Sect monitored the battle between Azaroth and the beasts from their stronghold. They used an Artifact that allowed them to gaze at a great distance.
Even with this artifact, they didn't exactly know how the battle between Azaroth and the beasts went on. This was due to the presence of that blizzard around them.
It blocked their sight and prevented them from figuring out what happened during the battle. When the Blizzard dispersed, they saw frozen bodies of the beasts at that spot.
The entire Night Mountain Sect was flabbergasted when they heard this information. A single 5 Star Warrior went up against all the strong Beast Races residing on this mountain and won?!
This was too shocking to be true! But the facts were up on the table. They had to believe it no matter how appalling it may seem.