Iron Crab
This large crab appears to be completely made of metal.

Iron Crab (CR 7; XP 3,200)
N Medium magical beast (aquatic)
Init +0; Senses darkvision 60 ft., low-light vision; Perception +10
AC 20, touch 10, flat-footed 20
(+10 natural)
hp 76 (8d10+32)
Fort +10, Ref +6, Will +1
DR 5/wood; Immune poison, pressure; Resist cold 10; SR 18
Speed 20 ft.
Melee 2 claws +10 (1d6+4 plus grab plus poison)
Special Attacks constrict (1d6+4)
Spell-Like Abilities (CL 8th; concentration +7)
1/day—iron body
Str 19, Dex 10, Con 19, Int 14, Wis 9, Cha 9
Base Atk +6; CMB +10 (+14 grapple); CMD 20 (32 vs. trip)
Feats Ability Focus (poison), Power Attack, Skill Focus (Craft [jewelry]), Weapon Focus (claw)
Skills Climb +15, Craft (jewelry) +13, Perception +10 (+18 gems and metals), Swim +15; Racial Modifiers +8 to Perception for gems and metals
SQ amphibious
Language Aquan, Trench
Environment aquatic
Organization solitary
Treasure double (only metals and gems)
Special Abilities
Metallic Poison (Ex) Claws—injury; save Fort DC 20; frequency 1/round for 6 rounds; effect 1d3 Dex damage; cure 2 saves

Found on the ocean floor near hydrothermal vents, these creatures resemble large crabs with a thick coat of metal over their shell. The shell is built up of armor plating shaped from minerals collected around hydrothermal vents. Iron crabs look like a drunken metal smith made them. Ungainly, nonsymmetrical, and badly balanced, they appear more humorous than threatening—but they are far more dangerous than their appearance suggests.

Iron crabs are the preeminent metallurgists of the seas. They are intelligent creatures, well versed in gems, precious metals, jewelry and similar items. They spend their days scouring the ocean floor for minerals and gemstones, hiding away their findings in their cave lairs until they have a vast horde of unworked metal and gemstones.

Iron crabs then go on a crafting spree, transforming their hoard into fine pieces of art. Once the horde is all finished goods, the crabs seal up their cave and go looking for a new one, starting the cycle of gathering and crafting all over again. It usually takes a century to build up a hoard of sufficient size and craft it all into jewelry. No one knows what drives the creatures to do this, or why they leave behind vast storehouses of wealth in their caves just to start all over again with nothing.

Because of their hoards, iron crabs are often sought out by nefarious sorts hoping to steal their vast wealth. They do not share with others, however, unless they are done a great service, shown great respect, or taught something new about metallurgy.

On Porphyra
Given the gift of metal bonding by Elementalist Lords, iron crabs served a mercenary role in the NewGod Wars, in the waters surrounding the Rainbow Isles.