Cairn stones sitting off the beaten path curse those passing within 5 yards of them.
Detect: Per-based Thaumatology, or Perception + Magery for mages, at -6.
Circumvent: Automatic (don't go within 5 yards of the trap).
Evade: Will at -3.
Effects: Any sentient (racial IQ 8+, no Bestial) within 10 yards of the trap who is not a frogman gives off light like a lantern for 1 hour for each point by which he missed the resistance roll. This makes stealth almost impossible; -10 to Stealth and Camouflage while the curse is in effect.