Pagan: Super Green

It would be nice if this door would just stay open. I start this session by returning to the Upper Catacombs, which I don't think I fully explored last time. Following the rightmost wall pattern, I first come to a door to the Lower Catacombs. It's locked, but it opens with my Key of the Scion, which being a staff instead of an actual key, doesn't go on the same key ring that I can use for every other key. The Lower Catacombs that I enter do not seem to be the same place I visited before (by falling down a pit). It's a maze of columbaria and bones, cracked floors showing lava underneath, fireballs shooting constantly from hidden spouts on the walls (why?). Levers open gates as I move forward. Skeletons stand as sentinels against the walls but rarely attack. This doesn't seem right. Continuing to follow the right wall, I come across a door flanked by two skeletons and a fireball spitter. The door closes as I get near, but I'm able to open it again. Unfortunately, I cannot get through…