"I don't want to know what you want with any universe," he clarifies uneasily. "Especially your own."

He could never buy into the mentality that Daniel's is the only universe of consequence, and he should somehow cease to care about what causality may exist in others. True, Lucifer's universe sounds like a desolate, grim place - that doesn't mean he wants to add to that by allowing him some way to slip back into it.