Istredd does sense the moment Lucifer enters the library, but he does go back to being distracted because that could mean anything. Usually he does find Istredd but sometimes he does his own thing as well, but there is an awareness that tingles up his spine and makes him smile privately. They spend so much time together now in the Nether and yet he mentally vibes warmth at him, no need to make a formal hello when they bleed (safely) into one another. When Lucifer is with him, his white wings automatically form themselves, which rarely happens in the library but his presence instinctively sets it off.

"Mmm?" Is his response though when Lucifer does appear to scatter what he's working on. He rolls his eyes although it is difficult to tell that is what he is doing when his eyes are glowing blue and without pupils these days. Lucifer knows that is what he is doing. His exasperation can be felt and he turns from what he's doing to watch him. Luckily Lucifer knows better than to disorganize anything. Yes, he can fix it easily, that isn't the point!

"Mmmmm." He says after considering what Lucifer is probably saying. He does make a list in his head of what he's blessed lately. Nothing that stands out. Istredd doesn't know if mortals have figured out that he is easy to sneak things past, or that they simply believe he supports their endeavors, shady or not. Probably the latter. Oops.

"That's why I have a list of suspicious humans. Although ... I may not have looked at it." Double oops.