Rhinoceros, Magma Element* (CR 6)

Large Elemental (Earth, Extraplanar, and Fire)
Alignment: Neutral
Initiative: -1 (Dex); Senses: darkvision 60 ft., low-light vision, Listen +14, and Spot +3

AC: 18 (-1 size, -1 Dex, +10 natural), touch 8, flat-footed 18
Hit Dice: 8d8+40 (76 hp); DR: 5/magic
Fort +11, Ref +5, Will +3
Speed: 30 ft.
Space: 10 ft./5 ft.
Base Attack +6; Grapple +19
Attack: gore +14 melee
Damage: melee gore 2d6+13 plus 1d6 fire
Special Attacks/Actions: powerful charge, heat
Abilities: Str 28, Dex 8, Con 21, Int 2, Wis 13, Cha 2
Special Qualities: Elemental traits (Immune to critical hits, fire, flanking, paralysis, petrification, poison, sleep effects, sneak attacks, stunning), vulnerability to cold
Feats: Alertness, Endurance, Improved Natural Attack (gore),
Skills: Listen +14 and Spot +3
Advancement: 9-12 HD (Large); 13-24 (Huge)
Climate/Terrain: Elemental Plane of Earth and Elemental Plane of Fire
Organization: Solitary
Treasure/Possessions: None

Source: Dragon #347

Heat (Ex): A magma element rhinoceros deals an additional 1d6 points of fire damage with its natural weapons.

Powerful Charge (Ex): In addition to the normal benefits and hazards of a charge, this ability allows a magma element rhinoceros to make a single gore attack with a +2 bonus that deals 1d6 points of fire damage.

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.