Since you can't see the night blades you can't be sure what they are doing unless you have a magical resource you wish to use.
This also means they don't have line of sight on you either, btw.
I guess you could try to lure them further into the foyer or push them back in order to get line of sight.
I guess Canthus knocked Phaserip after you took your turn, I'll just pretend you went after him and got a glimpse at where they moved to.