Then he'll be gone, as quickly as he appeared. Whether it's through slipping out of the summoning spell purely by being given permission or him taking off through the shadows too quickly to be seen, it doesn't really matter. He's just gone, leaving only the smoldering remains of the cigarette crushed against the coffee table to prove he was ever even here at all.

He even lets Strange get the last word for once with how fast he departs, not even uttering further threats or mocking him.

Though he does wonder if he might not find all these plants in the Rose Queen's realm. If he can't bring Strange to the Rose Queen, well, he never forbade the other way around, now did he?