Glass Sentry
CREATURE 6Variant elite sand sentry
Shifting back and forth between a detailed likeness of a human and a muted and featureless bipedal form, this creature of pure sand moves with an eerie grace. The sand sentry is often called upon by spellcasters to stand guard over an area of great importance-these elementals are patient participants in such roles, making them well suited for long-term service.
Tremorsense allows a monster to feel the vibrations through a solid surface caused by movement. It is an imprecise sense with a limited range (listed in the ability). Tremorsense functions only if the monster is on the same surface as the subject, and only if the subject is moving along (or burrowing through) the surface.
When the sand sentry takes fire or lightning damage, its outer layer of sand fuses into sheets of hardened glass for 1 minute. This increases the sand sentry's AC to 26 and grants it resistance 5 to acid, cold, electricity, fire, force, piercing, and slashing damage. A sand sentry can't use earth glide while glass armor is active.
A sand sentry can Burrow through earthen matter, including rock. When it does so, it moves at its full burrow Speed, leaving no tunnels or signs of its passing.