"Closing The Domain" 

Code-L stole the 'straw', stole the 'water' from another 'bottle', and then used their 'brand-new bottle' to let her own 'water' mix with their 'water'. 

This means the demons and the Valkyries would be mixed into one space. 

And the elders didn't think that their domain could still stay intact. 

Maybe the domain would be destroyed after a few minutes, and everything would be over! 

If, at that time, the summoned Valkyries were forced to return because they lost the domain and the demons also returned, that's good. 

But what if...what if before the demons returned, Code-L opened her own domain to let the demons stay? 

At that time, the situation would be reversed, and the celestials would be done for. 

The ten celestial elders didn't think that Code-L also had a unique physique like them, but they were already terrified of any possible future.