This is of course assuming that the area behind this particular door was not actually cleared and they find themselves fighting something when Greyview reaches them.

Also I'm pretty sure it'll just be a minor blip, if that; Greyview seems more than intelligent enough to figure out an alternative mode of communication once he's within Oona's darkvision range. But I find the idea of Redcloak's/Xykon's spells suddenly not working in the fact of a threatening opponent turning a few gears in their heads (and also kinda funny).