Dragon, Rattlyr, Great Wyrm (CR 20)

Gargantuan Dragon (Fire)
Alignment: Always lawful evil
Initiative: +0; Senses: blindsense 60 ft., darkvision120 ft., low-light vision, keen senses, and tremorsense 60 ft.
Languages: Draconic, Common, and various regional tongues

AC: 30 (-4 size, +24 natural), touch 6, flat-footed 30
Hit Dice: 35d12+245 (472 hp); DR: 15/magic
Fort +26, Ref +19, Will +27
Speed: 60 ft., burrow 30 ft.
Space: 40 ft./15 ft.
Base Attack +35; Grapple +60
Attack: 1 bite +48, 2 claws +43, 2 wings +43, 1 tail slap +43, 1 crush +43, 1 tail sweep +43
Damage: 1 bite 4d6+13, 2 claws 2d8+6, 2 wings 2d6, 1 tail slap 2d8, 1 crush 4d6, 1 tail sweep 2d6
Special Attacks/Actions: Breath weapon 2d6 (13)
Abilities: Str 37, Dex 11, Con 25, Int 28, Wis 27, Cha 26
Special Qualities: Resistance to electricity 20, immunity to fire, rattle, Hood extension, CL 15th, SR 23, Fear aura (DC 35)
Feats: #Feats: 12
Skills: Skill points: 321
Advancement: 40+ HD (Gargantuan)
Climate/Terrain: Warm deserts
Organization: Solitary (1 dragon, any age), clutch (1d4+1 wyrmlings, very young, young, juvenile, or young adults), family (pair of mature adults and 1d4+1 offspring)
Treasure/Possessions: Double standard

Source: Shining South

Breath Weapon (Su): A rattelyr has one type of breath weapon: a cone of fire.

Rattle (Su): A rattelyr can employ the rattle on its tail as a standard action. Any non-dragon within 240 feet of the rattelyr must make a Will save (DC 10 + 1/2 the rattelyr's HD + its Cha modifier) against this sonic, mind-affecting ability or become panicked for 4d6 rounds. Those with 5 or more HD are shaken for 4d6 rounds instead. A creature that makes the Will save cannot be affected by the same dragon's rattle for one day. All creatures (including dragons) that are within range and can hear the rattle must make a DC 15 Concentration check to employ any spells or spell-like abilities for as long as the rattling noise lasts.

Hood Extension (Su): A rattelyr can extend its hood as a free action. When fully extended, the hood reflects spells as if the rattelyr were affected by spell turning (as the spell). The dragon can reflect as many levels of spells per day as it has Hit Dice.

Tremorsense (Ex): Rattelyrs can automatically sense the location of anything within 60 feet that is in contact with the ground.

Skills: Climb, Hide, Jump, and Move Silently are considered class skills for rattelyrs. They have a +8 racial bonus on Spot checks and a +8 racial bonus on Hide checks in sandy terrain or in areas of loose dirt.

Fire Subtype

A creature with the fire subtype has immunity to fire. It has vulnerability to cold, which means it takes half again as much (+50%) damage as normal from cold, regardless of whether a saving throw is allowed, or if the save is a success or failure.