Aperture

Steep cliffs hall a barren valley at whose center is a crumbling, circular archway lathed in mind-breaking elder sigils and cryptic reliefs. Inside the circle, illusions phase in and out, an everchanging display of different places in time.
Deeper: This site has drawn a permanent sect of ritual inquisitors and apostate monks, both groups obsessively studying the aperture’s mysteries and how it may be controlled. Their camps dot the landscape alongside those of repentant pilgrims, the desperate, the cursed, the blighted, and the injured who have come to seek divine intervention.
None of these groups knows that this is a Well-spring Gate to the Underneath. The aperture is the key to “lock-in” one of many Underneath locations.
In the cooler evening hours, canyon trails to the camps becomes a hunting ground for desert bandits who prey on those traversing the area, launching surprise attacks to seize what meager valuables and supplies the pilgrims have.