Dungeons have feelings too!
This is kind of building upon my dynamic reaction roll idea. Instead of a static 1-in-6 chance of a wandering encounter, keep track of Dread . Dread represents the spirit of the dungeon catching onto the party as they explore. Think of a dungeon less as an ecosystem or stronghold, and more the domain of a territorial spirit who wants to keep intruders out. You might roll 2d6 for the dungeon's initial Dread , or you might just start at 2. Increase Dread by 1 each turn, up to 12. Past certain thresholds, the dungeon's presence will become more noticeable and threatening. At 6, the party might hear echoes or hums. At 10, there might be footsteps or chanting. Anything that freaks people out, and even better if it's specific to the environment. Every three turns, roll 2d6. If you roll below or equal to Dread , a random encounter is triggered. A random encounter is guaranteed to be triggered when Dread equals 12. When the party rests, roll d6 and reduce Dread by that much. Yo