Black Rock Triskelion (CR 18)
AC: 30 (-1 size, -1 Dex, +22 natural), touch 8, flat-footed 31
Hit Dice: 26d8+260 (377 hp); DR: 10/adamantine and magic
Fort +27, Ref +9, Will +11
Speed: 20 ft. and Burrow 20 ft.
Space: 10 ft.; Reach 10 ft.
Base Attack +19; Grapple +34
Attack: Melee: 3 piercing arms +30 each (2d6+11/19-20/x4); Ranged: 6 spikes +17 each (1d8+11/x3)
Attack Options: Cleave, Great Cleave, Power Attack, magic strike, metal strike
Abilities: Str 33, Dex 8, Con 31, Int 5, Wis 12, Cha 8
Special Abilities: fast healing 5
Special Qualities: Elemental traits: (immune to critical hits, electricity, flanking, paralysis, petrification, poison, sleep effects, sneak attacks, stunning), can't be tripped. SR 23; Resist: endure pain, stability (+8 against bull rush or trip); Weakness: vulnerability to sonic
Feats: Alertness, Cleave, Great Cleave, Great Fortitude, Improved Critical (piercing arm), Iron Will, Lightning Reflexes, Power Attack, Weapon Focus (piercing arm),
Skills: Climb +20, Listen +13, and Spot +13
Advancement: 27-40 HD (Large)
Climate/Terrain: Any Earth Temple Ogremoch orders it to defend
Monster Manual IV
The avatars of Elemental Evil have only recently appeared. Each avatar is the living will of an Prince of Elemental Evil. It contains a tiny fragment of the corresponding prince's essence and exists solely to advance its creator's cause on the Material Plane. The avatars gather at important sites such as recently discovered elemental nodes or other places that might be key to returning the Eye to the world. Sometimes they serve as mighty engines of war for the clerics of the Elder Elemental Eye.
The simmering war between each faction of the Elder Elemental Eye's priests draws in the avatars as well. These creatures are just as likely to turn against each other as they are to ally against a powerful threat.
A black rock triskelion is a powerful elemental creature spawned by Ogremoch, the Prince of Evil Earth Elementals. It smashes its enemies with three powerful arms that pierce armor and flesh like heavy picks.
Elemental Traits: Immune to poison, sleep, paralysis and stunning. Not subject to critical hits.
Endure Pain (Ex): Whenever a black rock triskelion fails a Reflex or Will saving throw against an effect that deals damage, it takes half damage if it succeeds on a Fortitude saving throw against the same DC. This additional saving throw affects only damage, not any other conditions that might apply from failing the original save.
Stability (Ex): A black rock triskelion is exceptionally stable on its feet. It gains a +8 bonus on ability checks made to resist being bull rushed or tripped when standing on the ground (but not when climbing, flying, riding or otherwise not standing firmly on the ground).
Metal Strike (Ex): A black rock triskelion's natural attacks are treated as adamantine, cold iron, and silver for the purpose of overcoming damage reduction.
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.
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.