Dragon, Topaz Very Old (CR 20)

Huge Dragon (Water)
Alignment: Always chaotic neutral
Initiative: +0; Senses: blindsense 60 ft., darkvision120 ft., low-light vision, and keen senses
Languages: Draconic

AC: 37 (-2 size, +29 natural), touch 8, flat-footed 37
Hit Dice: 31d12+186 (387 hp); DR: 15/magic
Fort +23, Ref +17, Will +24
Speed: 40 ft., fly 150 ft. (poor), burrow 5 ft., swim 60 ft.
Space: 15 ft./10 ft. (15 ft. with bite)
Base Attack +31; Grapple +50
Attack: 1 Bite +40, 2 claws +35, 2 wings +35, 1 Tail Slap +35, 1 crush +35 melee; Breath +40 ranged
Damage: 1 bite 2d8+11, 2 claws 2d6+5, 2 wings 1d8+5, 1 tail slap 2d6+16, 1 crush 2d8+16, Breath weapon 18d8 (31)
Special Attacks/Actions: Breath Weapon 18d8 (31); fear (DC 32), SR 27
Abilities: Str 33, Dex 10, Con 23, Int 24, Wis 25, Cha 24
Special Qualities: Cold immunity, water breathing, feather fall, fog cloud, control winds
Feats: #Feats: 11
Skills: Skill points: 223
Advancement: 32-33 HD (Huge)
Climate/Terrain: Inner Planes, any aquatic
Organization: Solitary, pair, or family (1-2 and 2-5 offspring)
Treasure/Possessions: Double Standard

Source: Monster Manual II

Breath Weapon (Su): A topaz dragon breathes a cone of dehydration that looks like a watery blast. When directed against an aqueous liquid (water or a liquid composed mainly of water), this effect evaporates one cubic foot of water per hit point of damage dealt. Each creature within the cone takes the indicated damage (18d8), or half that amount with a successful Reflex save (DC 31). Using a breath weapon is a standard action. Once a dragon breathes, it can't breathe again until 1d4 rounds later. A blast from a breath weapon always starts at the dragon's mouth and extends in a direction of the dragon's choice.

Frightful Presence (Ex): A very old dragon can unsettle foes with its mere presence. The ability takes effect automatically whenever the dragon attacks, charges, or flies overhead. Creatures within a radius of 270 feet are subject to the effect if they have fewer HD than the dragon (31 HD).

A potentially affected creature that succeeds at a Will save (DC 31) remains immune to that dragon's frightful presence for one day. On a failure, creatures with 4 or fewer HD become panicked for 4d6 rounds and those with 5 or more HD become shaken for 4d6 rounds.

Dragons ignore the frightful presence of other dragons.

Water Subtype

This subtype usually is used for elementals and outsiders with a connection to the Elemental Plane of Water. Creatures with the water subtype always have swim speeds and can move in water without making Swim checks. A water creature can breathe underwater and usually can breathe air as well.