"Hm. That doesn't match with the Lucifer I know. But we're from different worlds, I suppose." He eyes the Doctor skeptically, because people should be wary of Lucifer, if not terrified.

Donna's more fun to talk about, though, even with Balthazar's feeling of subtle uncertainty. He shakes his head. "I am who and what I am, and I have no idea whether affection between a human and an angel is sustainable in any fashion. But you can rest assured I'll do my best to look after her while she's here, and while I'm here."