It's faint. Just a shimmer, just a hint - just a suggestion that something is being stored within it, some kind of connection is being made. But in a darkened room like this, that faint and growing glow is enough for a thin smile to cross Xeha's lips.

"The impression's taking. A little longer and I think we'll be able to switch to the darkness imprint."

A subject which, if he's honest with himself, he's more than a little worried about. He's spent so long trying to avoid working with the dark more than he has to - and this is one of those subjects for which he's had to.
(And it's felt too easy to do so.)