At the end of the day, Ava wasn't able to understand why someone would create a plane and a secret magick circle that would double as a protective trap or a protective barrier.
If one would carefully think about it, the one who created this plane could control it. So, making a magick circle wouldn't make any sense at all. Unless of course, they were using this plane as some sort of a mask to hide another plane?
Does that even make any sense?
It didn't take too long before they were able to clear out the rest of the stuff inside the laboratory and even save Ulva.
Ava's only regret was the fact that they weren't able to save the others like Amelia and her child. It seems that the robed man was able to transfer them using a special tool that was created using their magick. It was kinda similar to a portal except this one was using the bodies of the witches that Ava first saw when she arrive in this place.