Golem, Ironwyrm (CR 17)

Large Construct
Alignment: Always neutral
Initiative: -1 (Dex)
Languages: Cannot speak

AC: 40 (-1 size, -1 Dex, +32 natural), touch 8, flat-footed 40
Hit Dice: 40d10 (220 hp); DR: 15/magic and adamantine
Fort +13, Ref +12, Will +14
Speed: 30 ft.
Space: 10 ft./5 ft.
Base Attack +30; Grapple +49
Attack: Bite +44 melee
Full Attack: Bite +44 melee and 2 claws +39 melee and 2 wings +39 melee and tail slap +39 melee
Damage: Bite 2d10+15, claw 2d8+7, wings 2d6+7, tail slap 2d8+22
Special Attacks/Actions: Breath weapon
Abilities: Str 41, Dex 8, Con -, Int -, Wis 13, Cha 19
Special Qualities: Construct traits, immunity to magic, immunity to rust
Feats: -
Skills: -
Advancement: 41-60 HD (Large); 61-80 HD (Huge)
Climate/Terrain: Any
Organization: Solitary
Treasure/Possessions: None

Source: Draconomicon

Breath Weapon (Su): 60-ft. cone, every 1d4 rounds, 20d10 fire, Reflex DC 30 half. The breath weapon type remains the same regardless of the dragon spirit contained within.

Immunity to Magic (Ex): An ironwyrm golem is immune to all spells, spell-like abilities, and supernatural effects, except as follows. A cold effect slows it (as the slow spell) for 3 rounds, with no saving throw. A fire effect breaks any slow effect on the golem and cures 1 point of damage for each 3 points of damage it would otherwise deal. For example, an ironwyrm golem hit by a delayed blast fireball cast by a 15th-level wizard that would normally deal 52 points of damage instead gains back 17 hit points. The golem gets no saving throw against fire effects.

Immunity to Rust (Ex): An ironwyrm golem is immune to rust attacks, whether magical or not.

The ironwyrm golem softens up foes with its fiery breath and then uses its formidable strength to destroy its foes in melee. It can even use this breath weapon on itself, in order to restore hit points or negate slow effects.