Dragon, Green Wyrm (CR 21)

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

AC: 40 (-4 size, +34 natural), touch 6, flat-footed 40
Hit Dice: 35d12+280 (507 hp); DR: 20/magic
Fort +27, Ref +19, Will +24
Speed: 40 ft., fly 200 ft. (clumsy), swim 40 ft.
Space: 20 ft./15 ft. (20 ft. with bite)
Base Attack +35; Grapple +60
Attack: 1 Bite +44, 2 claws +39, 2 wings +39, 1 Tail Slap +39, 1 crush +39, 1 Tail sweep +39 melee; Breath +44 ranged
Damage: 1 bite 4d6+13, 2 claws 2d8+6, 2 wings 2d6+6, 1 tail slap 2d8+19, 1 crush 4d6+19, 1 tail sweep 2d6+19, Breath weapon 2d6 (35)
Special Attacks/Actions: Breath weapon, fear (DC 32), SR 28
Abilities: Str 37, Dex 10, Con 27, Int 20, Wis 21, Cha 20
Special Qualities: Plant growth, Suggestion, Acid immunity, water breathing, CL 15
Feats: #Feats: 12
Skills: Skill Points: 385
Advancement: 36-37 HD (Gargantuan)
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 35) 22d6 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).