A tremor ward takes up an entire square. Each tremor ward radiates a continual 20-square close burst that flows into the earth. Though these wards are attuned to ignore natural burrowing animals, they can detect any break in the ground large enough to let a Small creature pass through it.
Consisting of elaborate runes placed on enchanted stones set into the ground, tremor wards detect major disturbances in the ground that indicate a breach large enough to let enemies through.
When a tremor ward detects a break in the ground, a path of runes leading from the Citadel Arcanum to the site of the breach glows brightly, allowing members of the city guard to follow the shortest path to the breach. The tremor wards can be deactivated by special request, such as when a new tower is to be built and ground needs to be broken, but most inhabitants of Mithrendain know better than to go digging within the reach of the tremor wards.