The Dark Domain is only called dark because it is named after the image of darkness, and it has nothing to do with the faith of the Dark Goddess.
When a mage's realm reaches the Golden Triangle Level, their thinking undergoes a qualitative change. At this time, a Golden Mage becomes an independent entity, capable not only of establishing a Life Barrier to shun knowledge but also of reshaping space with their vast thoughts.
Wayne had experienced Philomena's Dark Domain and often traveled around, so he was not unfamiliar with the surrounding environment.
The difference is, Wayne trusted Philomena very much, but as for Saina...
Don't be fooled by the fact that Saina was his teacher's teacher. When it comes to trust, she has a hard time even holding Philomena's shoes.
In the center of the Dark Domain, there is a white palace resembling a place for the veneration of faith.