The truth is that though their bond is open both ways, Lucifer has more bleed over than he does, especially with memories. His mind works this way, and Istredd likes that about it. It gives him full pictures, rather than slivers. He has to relinquish some of his personal control to do the same. Such as his longing to reach out, to comfort, to fix something that can't be fixed, and how he struggles to hold back.

If there is a way to anchor you here, I'll find it, so you never have to go back.

Istredd knows he can't get to the spell that brought them here, they have kept it hidden well, although the fact the other two nations had it in their pocket, it must be somewhere within reach. But perhaps finding a different angle will help. Anchoring him here would make it more difficult for the Singularity to toss him. Or would it? The promise is genuine at least and Istredd will try.