Buy me a coffeeEurypterid, the Dread Sea Scorpion
The Eurypterid crushes its prey with deadly pincers in the ancient seas — a real-life prehistoric sea monster!
The Eurypterid is a formidable prehistoric arthropod with a sleek, segmented exoskeleton that can range from just a few centimeters to over two meters in length, making some species among the largest arthropods to have ever lived. Its anatomy includes large, powerful pincers used for grasping prey, multiple pairs of jointed legs for walking or swimming, and a long, flexible tail spine that can act as a rudder or a weapon. The body is streamlined, aiding swift movement through water, and many species have specialized paddle-like limbs that allow for agile swimming, while others are more adapted to crawling along the seafloor. Their exoskeleton often displays ridges and spines, possibly for defense or camouflage among rocks and vegetation.
Eurypterids primarily inhabit shallow marine and brackish environments such as coastal lagoons, estuaries, and tidal flats. These habitats provide rich oxygenated waters and abundant prey, from small fish to other arthropods like trilobites and mollusks. Their behavior is largely predatory and opportunistic; they actively hunt smaller creatures but also scavenge when the chance arises. Utilizing their pincers, they seize and immobilize prey, while their sharp, spiny legs help them maintain grip on slippery surfaces or dig into sediment for ambush or escape.
Their modus operandi involves a blend of stealth and sudden bursts of speed. Often, Eurypterids lurk in hiding spots, using the environment to their advantage, before rapidly lunging at unsuspecting prey. Their flexible tails and powerful limbs enable quick maneuvers to capture and subdue targets, dragging them to the seafloor for consumption. Driven by instincts for survival and territorial dominance, Eurypterids constantly compete with other predators for food and shelter. Their role as apex predators in their ecosystems reflects a motivation rooted in maintaining their position within the food chain and ensuring reproductive success.
Eurypterid 5e
Lesser Eurypterid 5e
Greater Eurypterid 5e
Eurypterid 3.5
Eurypterid
Large monstrosity, unaligned
Armor Class: 15 (natural armor)
Hit Points: 102 (12d10 + 36)
Speed: 30 ft., swim 40 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 18 (+4) | 14 (+2) | 16 (+3) | 4 (–3) | 12 (+1) | 6 (–2) |
Saving Throws: Str +7, Dex +5
Skills: Perception +4, Stealth +5
Damage Resistances: Cold
Senses: Darkvision 60 ft., Tremorsense 30 ft., passive Perception 14
Languages: —
Challenge: 6 (2,300 XP)
Traits
Amphibious. It can breathe both air and water.
Keen Smell. The Eurypterid has advantage on Wisdom (Perception) checks that rely on smell.
Pincer Grip. When the Eurypterid successfully grapples a creature with its pincers, the target is restrained until the grapple ends.
Actions
Multiattack. It makes two attacks: one with its Pincers and one with its Tail Spike.
Pincers. Melee Weapon Attack: +7 to hit, reach 10 ft., one target.
Hit: 15 (2d8 + 4) bludgeoning damage. If the target is a creature, it must succeed on a DC 15 Strength saving throw or be grappled (escape DC 15).
Tail Spike. Melee Weapon Attack: +7 to hit, reach 15 ft., one target.
Hit: 12 (2d6 + 4) piercing damage. If the target is grappled, the Eurypterid can automatically hit with this attack and deals an additional 7 (2d6) piercing damage.
Legendary Actions
The Eurypterid can take 2 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The Eurypterid regains spent legendary actions at the start of its turn.
- Swift Swim. The Eurypterid moves up to its swim speed without provoking opportunity attacks.
- Pinch. The Eurypterid makes one pincer attack.
- Burrow Ambush (Costs 2 Actions). The Eurypterid burrows into sediment or under water debris, gaining advantage on its next attack roll.
Unique Traits & Tactics
Burrowing Predator. The Eurypterid can burrow into underwater sediment (difficult terrain for others) and remains hidden until it attacks, giving it advantage on initiative and surprise attacks.
Ambush Hunter. Prefers to wait patiently in shallow waters or mudflats to ambush prey. In combat, it uses hit-and-run tactics, striking with pincers to grapple and immobilize foes, then finishing with brutal tail spikes.
Territorial Instinct. If another Eurypterid enters its lair or hunting ground, it becomes aggressive and uses its environment to its advantage, including terrain to pin down enemies.
Ecology
Eurypterids are apex predators of prehistoric waters, combining brute strength, speed, and cunning in their hunt. They use stealth and burst swimming to capture prey, dragging it down into murky depths or burrowing into sediment to avoid threats.
The family to which Pentecopterus belongs, the Megalograptidae, was the first truly successful eurypterid group.
A scorpion the size of a crocodile skitters across the ocean floor.
Originally Posted by Shade of the En World forums.
Also known as “sea scorpions”, an eurypterid is an aquatic arthropod. They prey mainly on fish and other marine marine creatures, but have been known to attack humanoids on shorelines, dragging them beneath the surface.
| Eurypterid | |
| Medium vermin (Aquatic) | |
| Hit Dice | 3d8+3 (16 hp) |
| Initiative | +0 |
| Speed | 10 ft. (2 squares), Swim 20 ft. |
| Armor Class | 17 (+7 natural), touch 10, flat-footed 17 |
| Base Attack/Grapple | +2/+4 |
| Attack | Claw +4 melee (2d4+2) |
| Full Attack | 2 claws +4 melee (2d4+2) |
| Space/Reach | 5 ft./5 ft. |
| Special Attacks | Constrict 2d4+2, improved grab |
| Special Qualities | Darkvision 60 ft., tremorsense 60 ft., water dependent |
| Saves | Fort +4, Ref +1, Will +1 |
| Abilities | Strength 15, Dexterity 11, Constitution 13, Intelligence -, Wisdom 10, Charisma 2 |
| Skills | Hide +1 (+5 in sand or silt), Listen +1, Spot +2, Swim +11 |
| Feats | Endurance |
| Environment | Any aquatic |
| Organization | Solitary or pair |
| Challenge Rating | 2 |
| Treasure | None |
| Alignment | Always neutral |
| Advancement | 4–6 HD (Medium); 7-9 HD (Large) |
| Level Adjustment | – |
COMBAT
An eurypterid uses its tremorsense to locate prey in the water, then moves in for the kill.
- Constrict (Ex): An eurypterid deals automatic claw damage on a successful grapple check.
- Improved Grab (Ex): To use this ability, an eurypterid must hit with a claw attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it succeeds on the grapple check, it establishes a hold.
- Tremorsense (Ex): An eurypterid can detect and pinpoint any creature in the water within 60 feet.
- Water Dependent (Ex): Eurypterids can survive out of the water for 1 hour per 2 points of Constitution (after that, refer to the drowning rules on page 304 of the Dungeon Master’s Guide).
- Skills: An eurypterid has a +8 racial bonus on Swim checks. It can take 10 on a Swim check, even if distracted or endangered. An eurypterid can use the run action when swimming, provided it swims in a straight line. Eurypterids gain a +4 bonus to Hide checks when in sand or silt.
Originally found in Dragon #176, 1991.
Lesser Eurypterid
Medium monstrosity, unaligned
Armor Class: 13 (natural armor)
Hit Points: 45 (6d8 + 18)
Speed: 25 ft., swim 30 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 14 (+2) | 16 (+3) | 16 (+3) | 3 (–4) | 12 (+1) | 5 (–3) |
Saving Throws: Dex +5
Skills: Stealth +5, Perception +3
Damage Resistances: Cold
Senses: Darkvision 30 ft., Tremorsense 15 ft., passive Perception 13
Languages: —
Challenge: 2 (450 XP)
Traits
Amphibious. Can breathe air and water.
Keen Smell. Advantage on Wisdom (Perception) checks relying on smell.
Pincer Grip. Grappled creatures are restrained until escape (DC 13).
Actions
Multiattack. Two attacks: one with pincers, one with tail spike.
Pincers. Melee Weapon Attack: +4 to hit, reach 5 ft., one target.
Hit: 8 (1d10 + 2) bludgeoning damage; grapple DC 13.
Tail Spike. Melee Weapon Attack: +4 to hit, reach 10 ft., one target.
Hit: 6 (1d8 + 2) piercing damage; if target grappled, +4 (1d8) piercing damage.
Tactics
Uses hit-and-run ambush tactics in shallower waters or muddier environments, relying on agility to avoid retaliation. Uses burrowing to hide and surprise foes.
Greater Eurypterid
Huge monstrosity, unaligned
Armor Class: 17 (natural armor)
Hit Points: 210 (20d12 + 80)
Speed: 30 ft., swim 50 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 24 (+7) | 12 (+1) | 18 (+4) | 5 (–3) | 14 (+2) | 8 (–1) |
Saving Throws: Str +11, Con +8
Skills: Perception +6, Stealth +4
Damage Resistances: Cold, bludgeoning from nonmagical weapons
Senses: Darkvision 60 ft., Tremorsense 60 ft., passive Perception 16
Languages: —
Challenge: 12 (8,400 XP)
Traits
Amphibious. Breathes air and water.
Keen Smell. Advantage on Wisdom (Perception) checks relying on smell.
Pincer Grip. Grappled creatures are restrained until escape (DC 19).
Actions
Multiattack. Three attacks: two pincers, one tail spike.
Pincers. Melee Weapon Attack: +11 to hit, reach 15 ft., one target.
Hit: 22 (3d10 + 7) bludgeoning damage; grapple DC 19.
Tail Spike. Melee Weapon Attack: +11 to hit, reach 20 ft., one target.
Hit: 18 (3d6 + 7) piercing damage; if target grappled, +14 (4d6) piercing damage.
Crushing Slam (Recharge 5–6). The Eurypterid slams its massive body into a 15-foot cone. Each creature in the area must make a DC 18 Strength saving throw or be knocked prone and take 28 (6d8) bludgeoning damage, half damage on a successful save.
Legendary Actions
2 legendary actions, same as standard Eurypterid but also:
- Tail Sweep (Costs 2 Actions). The Eurypterid makes a tail spike attack against all creatures within 10 ft. (Dex save DC 18 for half damage, 18 (4d8) piercing damage).
Tactics
Uses brutal power and reach, preferring to grapple and crush prey. Will burrow to ambush and retreat underwater when threatened. Highly territorial and will defend lairs aggressively.