The cult had no wish to make it easy to enter their inner sanctum . . . and who can blame them? After all people, like me, want to kill them.
The best defense was an iron rail over a pit. I would tell you more, but I am thinking of using the cleared sanctum myself.
Razor Rail (CR 2) XP 400
This traps is a narrow metal rail crossing a pit or other drop, testing it will find it very stable (Acrobatic DC 15 to cross at speed, anyone can cross at the rate of 5′ per round). It almost imperceptibly narrows and then, using the reflective properties of the metal to disguise this, it becomes bladed.