>>712831567
It phases you through a solid object if there's an open space less than 25 feet away on the other side. You have to cast it on a physical object, it can't be something transparent. It can be used to bypass entire dungeon sections and an entire portion of the Orthmura mage's guild main quest, which also acknowledges that.

But yeah it's super finnicky. Great for a thief who knows his way around though.