The desire to keep secrets as secrets has left Adbrynu, my drow Celestial Warlock, in quite a title at times. Growing up in Menzoberranzan, he doesn’t feel comfortable sharing information about a very different lifestyle underground with his party. There have been times when it was just a matter of roleplay with no other real drawback. When it was officially revealed that another party member was wearing a wig, I had to ask myself whether Adbrynu would have figured it out. When I determined he did, it wasn’t hard for me to justify him not telling anyone. She’s wearing for a reason, right? It’s her decision, not Adbrynu’s. But there are also times when he would benefit greatly from sharing information when he hasn’t. Most recently, he had a curse placed on him by Lolth through a magic item. Adbrynu should have said something about his previous relationship with one of her priestesses. Instead, the party decided to capture a spider that was trying to kill him and pay a higher level Druid to Awaken it and figure out what was wrong that way. It cost us a particularly nice agate and an even nicer bottle of whiskey, but Adbrynu would have said it’s worth it to not share more of his secrets.
Heat, weather changes or brightness intensity, could all be used in loss of a title cycle. But astrology and climatology aren’t any areas I really look at very often. There are also very good stories by writers that take place in caves, underground labyrinths and dungeons. R.A Salvatore created the Menzoberranzan Narbondel. The arch-mage goes out and at the end of each day cycle resets the clock with a heated band, the denizens all have thermal vision to detect the changes as the “clock” winds the band to the top. A real-world functional would involve opening or closing a special partition of a material that absorbs but doesn’t dissipate easily that could be used as a visible gauge. Likely something with glass prisms set with various meltable materials or colour reactant liquids to indicate time/cycles.