He doesn't say it back--wouldn't give Istredd something Lucifer hasn't put the puzzle together for. It's enough reassurance that he doesn't need to though. That he can still figure out the pieces of himself while knowing that there's someone else willing to be on the other side of it, not forced out of necessity, what Thorne's done to all of them.

They both want to be here for each other not for obligation. He didn't really think that a possibility, ever.

"I do seem to remember, however," Lucifer says airily, "something about you promising to keep me warm." It's said lightly but it comes with an annoyed thought about Istredd sleeping under Lucifer's bed.

Sex? Eh.

Sleep? Mmmm.