Closed-door cultivation.
The portal exited at the bottom of the mountain, but unlike the front side of the mountain, which had a town at the base, the backside of the mountain had an extremely dense forest.
The trees grew at wild angles, creating a solid wall which would be impossible to pass through. The spiritual energy was almost as thick as it was in the inner court, but due to not wanting to attract too much attention, they placed formations around the entire forest to make it seem inconspicuous to anyone who flew over it.
The face of the mountain was much steeper than it was at the front too, almost looking like a cliff with thousands of cut outs in the stone. Cultivation caves.
In order to organize closed-door cultivation for the entire sect they needed individual spaces and carving them into the mountain was perfect. Each cave was just big enough to fit a single person sitting down. It was cramped but free from any and all distractions.