Hellfire Wyrm (CR 26)

Huge Dragon (Fire)
Alignment: Always lawful evil
Initiative: +4 (Improved Initiative); Senses: keen senses, Listen +34, and Spot +34
Languages: Draconic, Infernal, and Common, as well as the languages of any nearby humanoid races

AC: 36 (-2 size, + 28 natural), touch 8, flat-footed 36
Hit Dice: 23d12+184 (333 hp); DR: 15/epic
Fort +21, Ref +13, Will +21
Speed: 60 ft., burrow 30 ft., fly 250 ft. (clumsy)
Space: 15 ft./10 ft.
Base Attack +23; Grapple +40
Attack: Bite +30 melee and 2 claws +25 melee
Full Attack: Bite +30 melee and 2 claws +25 melee
Damage: Bite 2d8+9, claw 2d6+4
Special Attacks/Actions: Breath weapon, crush 2d8+13, frightful presence, spell-like abilities
Abilities: Str 29, Dex 10, Con 27, Int 23, Wis 26, Cha 28
Special Qualities: fiendish form, fire subtype, immunities, infernal aura, SR 37, summon baatezu
Feats: Cleave; Flyby Attack; Hover; Improved Initiative; Power Attack; Quicken Spell-Like Ability; Snatch; Wingover
Skills: Bluff +35, Diplomacy +37, Intimidate +37, Jump +47, Knowledge (arcana) +32, Knowledge (history) +32, Knowledge (religion) +32, Listen +34, Search +32, Spellcraft +34, and Spot +34
Advancement: 24-46 HD (Gargantuan)
Climate/Terrain: Any land and underground
Organization: Solitary, pair, or clutch (3-5)
Treasure/Possessions: Double standard

Source: Monster Manual II

Breath Weapon (Su): A hellfire wyrm can breathe a 50-foot cone of infernal flame that deals 14d10 points of damage. Each creature caught in the area can attempt a Reflex save (DC 29) to take half damage. One-half of the damage from this attack derives from infernal power and is therefore not subject to reduction by protective elemental magic. Once the wyrm breathes, it must wait 1d4 rounds before using its breath weapon again.

Crush (Ex): A flying hellfire wyrm can land on opponents three or more size categories smaller than itself as a standard action, using its whole body to crush them. A crush attack affects as many creatures as can fit under the wyrm's body. Each creature in the affected area must succeed at a Reflex save (DC 29) or be pinned, automatically taking 2d8+13 points of bludgeoning damage. Thereafter, if the wyrm chooses to maintain the pin, treat it as a normal grapple attack (grapple bonus +40). While pinned, the opponent takes crush damage each round.

Frightful Presence (Ex): When a hellfire wyrm charges, attacks, or flies overhead, it inspires terror in all creatures within 240 feet that have fewer Hit Dice or levels than it has. Each potentially affected opponent must attempt a Will save (DC 30). On a failure, a creature with 4 or fewer Hit Dice becomes panicked for 4d6 rounds, and one with 5 or more Hit Dice becomes shaken for 4d6 rounds. A successful save leaves that opponent immune to that hellfire wyrm's frightful presence for 24 hours. Dragons ignore the frightful presence effect of a hellfire wyrm.

Spell-Like Abilities: At will - blasphemy, charm person, demand, desecrate, dictum, fire storm, greater dispelling, hold person, improved invisibility, misdirection, pyrotechnics, sending, suggestion, teleport without error, true seeing (divine version), unholy aura, unhallow, wall of fire. Caster level 20th; save DC 19 + spell level.

Alternate Form (Su): A hellfire wyrm can assume the form of a Medium, Large, or Huge tiefling or outsider with the baatezu subtype.

Fire Subtype (Ex): A hellfire wyrm is immune to fire damage but takes double damage from cold unless a saving throw for half damage is allowed. In that case, it takes half damage on a success and double damage on a failure.

Immunities: A hellfire wyrm is immune to sleep and paralysis effects.

Infernal Aura (Su): Any creature within 5 feet of a hellfire wyrm automatically takes 5d4 points of fire damage per round. It can suppress this aura as a free action.

Keen Senses (Ex): A hellfire wyrm sees four times as well as a human in low-light conditions and twice as well in normal light. It also has darkvision with a range of 120 feet.

Summon Baatezu (Sp): Once per day, a hellfire wyrm may summon a single baatezu, cornugon, or gelugon with a 100% chance of success. This ability functions like a summon monster spell of the appropriate level. A summoned devil automatically returns whence it came after 1 hour. A baatezu that has just been summoned cannot use its own summon ability for 1 hour.

Feats: A creature that is flung by a hellfire wyrm after being snatched travels 100 feet and takes 10d6 points of damage. If the hellfire wyrm is flying, the creature takes this damage or the appropriate falling damage, whichever is greater.

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.