"Would you like us to help? Maybe we can have an undead bug stick to a guard there to tell us where he goes. Then we can grab him while he's sleeping and have you read his mind. Or just kill them and absorb their memories, though I'm worried that might put them on alert."
Ask something along those lines.
From what I understand, we can't really see through their eyes though. The best we can do is know their status. Hmm... Unless there's a way to extract memories from undead. Maybe we can experiment with that.
Do only living things form memories? Experiment with the mouse. Maybe if we animate it with a spirit we can then consume the spirit to gain some of the memories. Or maybe we can order the spirit to do a certain action we can sense upon certain events?
Also, can the spirit-animated skeletons speak better than Piecewise? I mean, can they answer questions? Can you hold a conversation with them? Would they be able to report something they've seen (like Esme doing something with her hands behind our back?).
Finally, can we transfer spirits? Can we put one in a body that's good for scouting and then move it to a skull so that it can report what it saw?
"Sneaking something undead in to spy for us isn't a terrible idea." Esme says, considering it, "But it does have a risk. Undead under someone's control have a connection to the necromancer, one that other necromancers can see. If there are other necromancers in that facility, which would not be surprising considering its apparent purpose, then they would recognize the spy as at least being an unknown undead. And remember that those connections lead straight back to you so they might be able to trace it."
You consider the problem of undead memories. You know that the servants do not gain memories, at least not ones you can eat on death. You've already found that out as a result of your chicken meddling. You reanimate the mouse with a spirit and then get Esme to secretly tell it something. You confirm that you cannot hear her or know what was said, and that at least in the mouse body the spirit cannot tell you. You attempt to eat the spirit but, unlike memories which are subsumed into you upon contact, the spirit is as solid and unassailable as any physical object.
You next repeat the experiment with the spirit animated skeletons and find that, at least in this form, they can tell you things. They are not, however, very intelligent. Conversations appear to be basically outside their capacity: They're nearly monosyllabic and will generally respond best to yes or no questions or questions with very straight forward answers. Repeating secret words goes just fine, but asking "What does Esme look like?" nets things like "female" or "weak" or the color of her skin, hair, or clothing. However, there is one interesting point. You animated the skeletons with whatever spirit you could get hold of at the time. Two are animated with quite small fish like things, but the third is animated by a larger crab like thing which was higher up and harder to grab. This spirit seems more capable: not as capable as a normal person but at least when asked "What does Esme look like" he responds "Adult human female"
Spirits can indeed be transferred, at least in theory. You pull the spirit from the mouse and hold it outside the body for a time before putting it back in. If this is possible, you don't see why switching two wouldn't be. It does bring up a point you hadn't thought of yet: Can multiple spirits be contained in one body? You don't remember reading about anything like that.
Esme yawns and says that if there's nothing else you'll need help with immediately, she's going to bed.