The breath weapon itself transmutes water into a milky, luminous solid matter similar to mother-of-pearl. Although the material is not ice and does not melt, it does evaporate under the same conditions as liquid water; exposed to air or sunlight, a mass of this material will eventually dissolve. While solid, the water has the same saving throws as wood of the same thickness. When the gas cloud contacts a stream, river, lake, or similar body of water, the water solidifies to a depth of one-half inch per age category of the dragon (3 inches for an adult, age category 6).
Water-based creatures such as water weirds and elementals must save vs. breath weapon or die. A surviving creature suffers 1d12 points of damage per age category and is slowed for 1d4 turns. The creature’s physical attack damage is increased by 50% for as long as it is slowed.
Creatures with a high water content (such as humans and demihumans) are also vulnerable to the breath weapon. The gas permeates the skin, making it crack and flake away like peeling bark, and causes severe trauma to organs and muscles. This has three effects (modified by a saving throw):
* Initial exposure to the gas causes 4d6 damage. Prolonged exposure does not inflict additional damage.
* The equivalent of a slow spell for one round per age category of the dragon.
* Additional damage while slowed: strenuous activity (running, melee) inflicts 1d8 per round, moderate activity (spellcasting, walking, firing a bow) inflicts 1d8-4 points of damage. No damage or negative damage means that a cast spell is not disrupted by pain.
A successful saving throw vs. breath weapon halves the initial damage and duration of the slow effect, but does not affect the additional damage of straining traumatized muscles.
Special Tactics: Prismatic dragons often lie in ambush in a lake or deep river, using their wings or waveform power (achieved at juvenile age) to drench prey. If a drenched prey fails a saving throw against the breath weapon, all saturated clothing, ahir, and so on hardens into a solid shell, much like a body cast. The shell must be broken before the victim can move again.
Wet surfaces that do not absorb water well (bare skin, leather, metal) will receive only a thin coating, as easily broken as an eggshell. Most people will have no trouble moving their hands or speaking.
Absorbent surfaces, such as normal clothing, must be shattered. A successful bend bars roll cracks the shell on one limb sufficiently to allow movement. An immobilized, statue-like victim can tip himself over, shattering the shell if it fails to save vs. crushing blow. No amount of tapping from within the shell can break it. A solid blow against AC 6 frees one limb or the torso if the shell fails its saving throw vs. crushing blow. The shell absorbs 5 points of damage, the rest affects the trapped victim. When one part of the shell shatters, the shell covering an adjacent limb is 50% likely to shatter as well.