Dragon, Obsidian Wyrm (CR 23)
AC: 42 (-4 size, +36 natural), touch 6, flat-footed 42
Hit Dice: 37d12+296 (536 hp); DR: 20/magic
Fort +28, Ref +20, Will +24
Speed: 40 ft., fly 200 ft. (clumsy), burrow 20 ft., swim 20 ft.
Space: 20 ft./15 ft. (20 ft. with bite)
Base Attack +37; Grapple +62
Attack: 1 bite +47, 2 claws +42, 2 wings +42, 1 tail slap +42, 1 crush +42, 1 tail sweep +42
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 22d10 (36)
Abilities: Str 37, Dex 10, Con 27, Int 35, Wis 19, Cha 18
Special Qualities: Fire subtype, planar travel, Firefall, Biofeedback, burning ray, Whitefire, wall of ectoplasm, Ectoplasmic armor, flaming shroud, Plane shift, mind store, SR 34, Fear aura (DC 32), Manifester level 17
Feats: #Feats: 13
Skills: Skill points: 450
Advancement: 38-39 HD (Gargantuan)
Climate/Terrain: Inner Planes, warm mountains, underground
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
Fire Subtype (Ex): An obsidian dragon is immune to fire but takes double damage from cold, except on a successful save.
Breath Weapon (Su): An obsidian dragon has one breath weapon: a cone of fire.
Planar Travel (Su): Obsidian dragons have the innate ability to pass instantly between the Material Plane and the Inner Planes, where they often make their homes.
Psionics (Sp): 3/day -- biofeedback, burning ray, ectoplasmic armor, firefall, flaming shroud, plane shift, wall of ectoplasm, whitefire; 1/day -- genesis, mind store. Manifester level varies by age; save DC d20 + appropriate ability modifier + power level.
Attack/Defense Modes: mind thrust/thought shield. An obsidian dragon manifests powers and gains additional attack and defense modes as if it were a psion with Metacreativity as its primary discipline.
Skills: An obsidian dragon has the Appraise skill for free at 1 rank per Hit Die.
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.