Scalder Crab

Medium construct, neutral

Armor Class 16 (natural armor)
Hit Points 83 (11d8 + 33)
Speed 10 ft., swim 20 ft.

19 (+4) 5 (-3) 17 (+3) 10 (+0) 13 (+1) 8 (-1)

Skills Athletics +7
Damage Resistances bludgeoning, piercing, slashing from nonmagical attacks that aren’t adamantine
Damage Immunities fire, poison
Condition Immunities charmed, exhaustion, paralyzed, petrified, poisoned
Senses darkvision 60 ft., passive Perception 11
Languages understands the languages of its creator but can’t speak
Challenge 6 (2,300 XP)
Proficiency Bonus +3


  • Adamantine Hide. A critical hit made against the crab becomes a normal hit instead.
  • Constructed Nature. The crab doesn’t require food or air.
  • Scorching Engine. The crab’s skin is boiling to the touch. Any creature that touches the crab, or hits it with an unarmed attack, takes 3 (1d6) fire damage, ignoring resistances to fire from being underwater. In addition, any item made of metal that touches the crab is instantly superheated. A creature that comes into contact with the item takes 5 (2d4) fire damage, ignoring resistances to fire from being underwater. If the item is being held or worn by a creature, the creature must succeed on a DC 14 Constitution saving throw or drop the item if it can. If the creature does not drop the item, it has disadvantage on attack rolls and ability checks until the start of its next turn, when the item cools again.
  • Unwieldy Form. If the crab is makes a Dexterity saving throw, and it fails by 5 or more, it is flipped onto its back, it must use its action to succeed on a DC 10 Dexterity check to right itself. While flipped, the crab has disadvantage on all attacks, its speed is reduced to 0, and it automatically fails Dexterity and Strength saving throws. The crab may also be flipped onto its back by other means, such as if it loses a Strength contest to another creature.


  • Multiattack. The crab makes three Claw attacks. It can replace one of the attacks with a use of Crush.
  • Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 9 (1d10 + 4) bludgeoning damage, and if the target is Medium or smaller, it is grappled (escape DC 14). At the start of a grappled target’s turn, it must make a DC 14 Constitution saving throw, taking 7 (3d4) fire damage on a failed save, or half as much damage on a successful one, ignoring resistances to fire from being underwater. Until this grapple ends, the target is restrained, and the crab can’t use this claw against other targets. The crab has two claws.
  • Crush. The crab crushes down on a creature it has grappled. The creature must make a DC 14 Strength saving throw. On a failed save, the creature takes 13 (3d8) bludgeoning damage, or half as much on a successful one.


Individual scalder crab sentries may be found up to a mile from their home vents. However, once a crab spots an intruder, it sends an electric signal, detectable only by other scalder crabs, alerting its kind to danger. All crabs within a 1-mile radius will come together to protect their home.

Crabs not actively defending their homes are otherwise docile and can often be observed cleaning their claws, watching fish swim by, or climbing atop one another for better purchase on rocky surfaces.


Down in the deepest ocean trenches lie the boiling fissures where scalder crabs make their homes. Very few individuals have ever encountered these 4-foot-long crustacean Constructs and even fewer have ever uncovered their true mechanical nature.

Stalwart Sentries. Scalder crabs, despite their uncanny resemblance to actual crabs, are not living beings. Instead, they are automatons left behind by an unknown forge master who once used the sea’s thermal vents as a mighty furnace. Today, the scalder crabs that remain are forgotten guards, dutifully awaiting their creator’s return.

Tough As Adamantine. Deep-sea darkness makes it difficult to realize that the scalder crab’s shells are adamantine. As a result, not only are these Constructs unphased by scalding temperatures, but they are also resilient to physical damage.

Heavyweight Hitters. The scalder crab’s hefty build can crush most objects without much effort. However, the crabs each weigh about 500 pounds, making them slow-moving and unable to float. Scalder crab fleets are so large that on land, they are nearly immobile. In addition, scalder crabs are very top-heavy. If flipped onto their backs, they often cannot right themselves and are left defenseless.

Steam-Powered. Scalder crabs are powered by long-lost artifice and a considerable amount of steam, making their shells scorching to the touch. In the presence of a scalder crab fleet, even the surrounding water becomes superheated.

Crustacean Camaraderie. The scalder crab lives by an ancient directive to guard the entrance to its forge. However, the GM can choose to allow characters to reprogram a scalder crab over time through Tinker’s Tools and Intelligence (Arcana) checks.

Section 15: Copyright Notice

Affinity Torus Copyright 2022 Dias Ex Machina Author Chris Dias

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