Don't Know
Ciel was silent for a long time after hearing her words.
In the end, he nodded to her.
"Alright," he said, then sent a portal into the Immortal Domain to her.
From his point of view, there was no way his mother was deceiving him or anything.
If there was such a thing, it wouldn't even be necessary with her powers.
Plus, she could create something like the Immortal Domain easily. It just didn't have the Saint Stone so it would need a constant supply of energy for it to last.
Of course, something like a puppet with the power of a God King would practically make his safety more assured.
The Ancient Night King accepted the portal then nodded to Ciel.
"It took me about a day to make it, now you can rest in this palace," she said.
"Perhaps, in two or three days Synthia will come to this city."
Whoosh!