Monolith, Magma (CR 17)

Gargantuan Elemental (Earth, Extraplanar, and Fire)
Alignment: Usually neutral
Initiative: -2 (Dex); Senses: darkvision 60 ft., Listen +43, and Spot +43
Languages: Ignan, Terran

AC: 24 (-4 size, -2 Dex, +20 natural) touch 4, flat-footed 24
Hit Dice: 36d8+252 (414 hp); DR: 15/-
Fort +27, Ref +10, Will +16
Speed: 30 ft.
Space: 20 ft./20 ft.
Base Attack +27; Grapple +55
Attack: 2 slams +40 melee
Damage: 2 slams 6d8+16/19-20 plus 3d6 fire
Special Attacks/Actions: heat metal
Abilities: Str 43, Dex 6, Con 24, Int 12, Wis 15, Cha 17
Special Qualities: elemental traits (Immune critical hits, fire, flanking, paralysis, petrification, poison, sleep effects, sneak attacks, stunning), vulnerability to cold
Feats: Alertness, Awesome Blow, Blind-fight, Cleave, Great Cleave, Improved Bull Rush, Improved Critical (slam), Improved Natural Attack (slam), Improved Overrun, Improved Sunder, Iron Will, Power Attack, Weapon Focus (slam),
Skills: Diplomacy +5, Intimidate +16, Jump +29, Listen +43, Sense Motive +15, and Spot +43
Advancement: 37-54 HD (Gargantuan)
Climate/Terrain: Elemental Plane of Earth and Elemental Plane of Fire
Organization: Solitary
Treasure/Possessions: None

Source: Dragon #347

Burn (Ex): A magma monolith's slim attack deals bludgeoning damage plus fire damage due to the creature's flaming body. Anyone hit by a magma monolith's slam attack must succeed on a DC 34 Reflex save or catch on fire. The flame burns for 1d4 rounds, dealing 3d6 points of fire damage each round. Unless it is still in contact with the magma monolith, a burning creature can take a move action to put out the flames. The save DC is Constitution-based. Creatures hitting a magma monolith with natural weapons or unarmed attacks take 3d6 points of fire damage and also catch on fire unless they succeed on a DC 34 Reflex save.

Earth Subtype

This subtype usually is used for elementals and outsiders with a connection to the Elemental Plane of Earth. Earth creatures usually have burrow speeds, and most earth creatures can burrow through solid rock.

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.