BoringKeys

Thanks for the welcome! No, there is a lantern just outside the double doors on the left. It's possible the monsters are spawning outside of the lantern's range. I'm working on getting more. I noticed the handbook, in the Temporal Stability guide, says that torchlight deters rift appearances, possibly implying that only torches have this effect. Do all light sources prevent rifts to different degrees? I guess I'm lacking understanding of the spawning mechanism. I only mean the spawn rules for the stairs and slabs in the image should be the same as the green highlighted floor. I thought the highlighted blocks indoors meant they had reduced or disabled monster spawning. Seems like I need to spend more time in the wiki. Thanks!

This is an image inside a highlighted, valid multi-story "room." Some blocks that aren't highlighted are able to spawn enemies if there is room above them. There are two floors above the pictured floor with slab floors. Both commonly spawn enemies even during low rift activity. I think it would be an improvement if the game was ( potentially barring special circumstances) completely unable to spawn enemies inside valid rooms. At the very least, it should consider slabs and stairs as non-spawning like full blocks. Shouldn't we be able to have stairs between floors inside a valid room without inviting enemies into our buildings?