Monolith, Fire (CR 17)

Gargantuan Elemental (Extraplanar and Fire)
Alignment: Usually neutral
Initiative: +13 (+9 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., Listen +43, and Spot +43
Languages: Ignan

AC: 29 (-4 size, +9 Dex, +14 natural), touch 15, flat-footed 20
Hit Dice: 36d8+216 (378 hp); DR: 15/-
Fort +20, Ref +29, Will +16
Speed: 60 ft.
Space: 20 ft./20 ft.
Base Attack +27; Grapple +50
Attack: Slam +35 melee
Full Attack: 2 slams +35 melee
Damage: Slam 6d6+11/19-20 plus 4d6 fire
Special Attacks/Actions: Burn
Abilities: Str 32, Dex 29, Con 22, Int 12, Wis 15, Cha 17
Special Qualities: elemental traits, immunity to fire, vulnerability to cold
Feats: Alertness; Blind-fight; Cleave; Combat Reflexes; Dodge; Great Fortitude; Improved Critical (slam); Improved Initiative; Improved Natural Attack; Iron Will; Mobility; Power Attack; Spring Attack; Weapon Focus (slam)
Skills: Balance +13, Diplomacy +5, Intimidate +16, Jump +25, Listen +43, Sense Motive +15, Spot +43, and Tumble +24
Advancement: 37-54 HD (Gargantuan)
Climate/Terrain: Elemental Plane of Fire
Organization: Solitary
Treasure/Possessions: None

Source: Complete Arcane

Burn (Ex): A fire monolith's slam attack deals bludgeoning damage plus fire damage because of the creature's flaming body. Anyone hit by a fire monolith's slam attack must succeed on a DC 34 Reflex save or catch on fire. The flame burns for 1d4 rounds. Unless it is still in contact with the fire monolith, a burning creature can take a move action to put out the flames. The save DC is Constitution-based.

Creatures that hit a fire monolith with natural weapons or unarmed attacks take fire damage as though hit by the monolith's attack, and also catch on fire unless they succeed on a DC 34 Reflex save.

Fire monoliths combine great physical power with incredible quickness and the ability to set their foes ablaze. Like other fire elementals, fire monoliths cannot enter water or any other nonflammable liquid, and so cannot cross water unless they can step or jump over it.

Extraplanar Subtype

A subtype applied to any creature when it is on a plane other than its native plane. A creature that travels the planes can gain or lose this subtype as it goes from plane to plane. This book assumes that encounters with creatures take place on the Material Plane, and every creature whose native plane is not the Material Plane has the extraplanar subtype (but would not have when on its home plane). An extraplanar creatures usually has a home plane mentioned in its description. These home planes are taken from the Great Wheel cosmology of the D&D game (see Chapter 5 of the Dungeon Master's Guide). If your campaign uses a different cosmology, you will need to assign different home planes to extraplanar creatures.

Creatures not labeled as extraplanar are natives of the Material Plane, and they gain the extraplanar subtype if they leave the Material Plane. No creature has the extraplanar subtype when it is on a transitive plane; the transitive planes in the D&D cosmology are the Astral Plane, the Ethereal Plane, and the Plane of Shadow.

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.