Emergency Potion

This thumb-sized vial is cut from clear crystal and stoppered with wax stamped by a tiny silver sigil. Inside swirls a liquid like liquid starlight, pale blue at rest and flashing gold whenever it senses nearby danger. Thin runes spiral through the glass and briefly drift into the air when the bottle is uncorked, then fade with a soft chime. The potion smells faintly of ozone, mint, and hot parchment.