Magmal Horror (CR 16)

Huge Elemental (Earth, Extraplanar, and Fire)
Alignment: Usually chaotic
Initiative: +3 (Dex); Senses: darkvision 60 ft., tremorsense 60 ft., Listen +22, and Spot +18

AC: 27 (-2 size, +3 Dex, +16 natural), touch 11, flat-footed 24
Hit Dice: 16d8+112 (184 hp); DR: 10/adamantine
Fort +19, Ref +15, Will +9
Speed: 20 ft., burrow 40 ft., swim 60 ft.
Space: 15 ft./10 ft. (20 ft. with tentacles)
Base Attack +12; Grapple +30
Attack: Tentacle +20 melee
Full Attack: 4 tentacles +20 melee and bite +18 melee
Damage: Tentacles 2d6+10 plus 2d6 fire, bite 2d8+5 plus 2d6 fire
Special Attacks/Actions: Constrict 2d6+15, heat, improved grab, swallow whole
Abilities: Str 31, Dex 16, Con 24, Int 10, Wis 19, Cha 8
Special Qualities: elemental traits, immunity to fire, resistance to sonic 10, vulnerability to cold
Feats: Cleave; Combat Reflexes; Great Fortitude; Lightning Reflexes; Multiattack; Power Attack
Skills: Jump +20, Listen +22, Spot +18, and Swim +18
Advancement: 16-32 HD (Huge); 33-48 HD (Gargantuan)
Climate/Terrain: Elemental Plane of Fire
Organization: Solitary
Treasure/Possessions: None

Source: Web

Constrict (Ex): A magmal horror deals 2d6+15 points of damage with a successful grapple check.

Heat (Ex): A magmal horror generates intense heat that melts earth or stone within 5 feet of its body into molten lava. Every creature and object within 10 feet of the creature takes 4d6 points of fire damage per round that it remains within this range (Reflex DC 25 half). Any creature that strikes a magmal horror with a natural attack or an unarmed strike takes 8d6 points of fire damage.

The heat that the magmal horror generates can also melt or char weapons. Whenever a weapon strikes a magmal horror, the user must make a successful DC 25 Fortitude save or the weapon is destroyed. Any enhancement bonus that the weapon has is applied to the saving throw as a bonus. The save DCs are Constitution-based.

Improved Grab (Ex): To use this ability, the magmal horror must hit an opponent at least one size category smaller than itself with a tentacle attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can constrict the same round or attempt to swallow the following round.

Swallow Whole (Ex): A magmal horror can try to swallow a grabbed opponent of a smaller size category than itself by making a successful grapple check. Once inside, the opponent takes 2d8+10 points of crushing damage and 20d6 points of fire damage from the magmal horror's blazing gullet. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal 25 points of damage to the gullet (AC 15). Once the creature exits, internal motion closes the hole; another swallowed opponent must cut its own way out. A Huge magmal horror's interior can hold 2 Large, 8 Medium, 32 Small, 128 Tiny, or 512 Diminutive or smaller opponents.

Skills: A magmal horror has a +4 racial bonus on Listen checks. A magmal horror gains a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

A magmal horror grabs opponents with its tentacles and attempts to either swallow them or plunge them into the lava that its body creates from the surrounding stone. Should foes prove resistant to fire, the magmal horror bludgeons them with its tentacles, then constricts them and thrusts them into its gaping maw.

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.