He offers a small, flabbergasted wave in return, because he knows what that thing could spout out of it in the wrong circumstances.

"Did that 'casual friend' give you particular care-taking rules?" he asks mildly. It's the Horizon, so it might not matter, but then Lucifer can also picture something going wrong in the Horizon again and just dozens of trouble-making parasites suddenly scattering across domains with Mat's as the source.

... Actually that would be hilarious.

Heh.