Everywhere in the dungeon the PCs go, they find little trails of slime, though they seem to only go directly down the middle of the hallway, in a straight line, until making turns at perfect right angles. A PC who makes a 4d6 roll under their Wisdom can hear a slight ticking sound, which seems to be coming from within the walls. Attempts to destroy the walls yield no information.
If they are still there at midnight, a series of chimes sound all around them. Tiny snails with clockwork shells slither out of holes all around the dungeon. They form a procession and move into the nearest room. Once there, they follow each other around in a circle for one minute, until a second chime sounds. They then return to the holes they slithered out from.