The consequence outweighed the potential gains Arachne could obtain. And with one more of his creatures out of the equation, that left Fenrir being the last recipient for the ember.
The moment Noah called Fenrir's name; the beast literally sprung from his seated position. if not for the feathered collar, the ground would've been easily destroyed from the force of his landing.
The tension during the moment Fenrir received the ember was even more daunting than the earlier battle. The depression and yet mildly resentment Arachne was releasing through her mana seeped uncontrollably around them.