Dragon, Green Very Old (CR 18)

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

AC: 36 (-2 size, +28 natural), touch 8, flat-footed 36
Hit Dice: 29d12+174 (362 hp); DR: 15/magic
Fort +22, Ref +16, Will +20
Speed: 40 ft., fly 150 ft. (poor), swim 40 ft.
Space: 15 ft./10 ft. (15 ft. with bite)
Base Attack +29; Grapple +48
Attack: 1 Bite +38, 2 claws +33, 2 wings +33, 1 Tail Slap +33, 1 crush +33 melee; Breath +38 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 2d6 (30)
Special Attacks/Actions: Breath weapon, fear (DC 28), SR 25
Abilities: Str 33, Dex 10, Con 23, Int 18, Wis 19, Cha 18
Special Qualities: Plant growth, Suggestion, Acid immunity, water breathing, CL 11
Feats: #Feats: 10
Skills: Skill Points: 290
Advancement: 30-31 HD (Huge)
Climate/Terrain: Temperate and warm forest and underground
Organization: Solitary, pair, or family (1-2 and 2-5 offspring)
Treasure/Possessions: Double Standard

Source: Monster Manual

Breath Weapon (Su): A green dragon has one type of breath weapon, a cone of corrosive (acid) gas (Reflex save for half damage DC 33) 20d6 acid damage. 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.

Water Breathing (Ex): The dragon can breathe underwater indefinitely and can freely use its breath weapon, spells, and other abilities while submerged.

Air Subtype

This subtype usually is used for elementals and outsiders with a connection to the Elemental Plane Air. Air creatures always have fly speeds and usually have perfect maneuverability (see the section on Movement).