Buy me a coffeeEogyrinus, Primeval Tide Stalker
“Meet Eogyrinus: the aquatic terror with a monstrous jaw, lurking in the swamps and ambushing prey with deadly precision!”
Eogyrinus reaches up to 4–4.6 m in length, with a slender, almost eel-like body and markedly reduced, paddle-like limbs that add little to propulsion but aid in minor steering. Its skull is broad and triangular, lined with sharp, conical teeth ideal for gripping slipping prey. The laterally flattened tail dominates locomotion, powering rapid lateral sweeps that propel its streamlined form through water. Skin texture may have been more scaly than moist, providing protection against dehydration in semi-aquatic life.
Behaviour
Eogyrinus is a solitary ambush predator, spending hours half-buried among submerged roots and vegetation. It remains perfectly still until unsuspecting fish or smaller amphibians drift within range, then accelerates in a burst of tail-driven speed. Some researchers propose it performed a crocodile-style death roll to tear larger prey apart once seized in its jaws.
Habitat
This genus inhabits the coal-swamp floodplains of Late Carboniferous Europe, around 315–312 million years ago, in waterways choked with dense weeds, submerged plant mats, and fallen logs. The murky, slow-moving channels provide perfect cover for its low-profile ambush strategy.
Modus Operandi
- Lie-in-Wait: Eogyrinus uses its slim profile and muted coloration to blend with roots and detritus.
- Tail-Powered Strike: A sudden lateral whip of the flattened tail launches it forward, closing distance in an instant.
- Clamp and Submerge: Its interlocking teeth clamp down, dragging prey beneath the surface to drown or dismember—sometimes augmented by a death-roll twist.
- Occasional Shore Foray: Though primarily aquatic, it may lunge onto muddy banks for prey at the water’s edge.
Motivation
Eogyrinus epitomizes an evolutionary arms race in Carboniferous wetlands: every feature—from reduced limbs and streamlined form to powerful tail and crushing jaws—is tuned for one purpose: dominate as the apex ambush predator and outcompete rivals in a crowded, primeval ecosystem.
Eogyrinus 5e
Eogyrinus 3.5
Eogyrinus
A 15-foot, eel-like leviathan slides beneath the murky surface, its triangular jaws and whip-like tail promising sudden, deadly force.
Large Beast, Unaligned
Armor Class 13 (natural armor)
Hit Points 110 (13d10 + 39)
Speed 20 ft., swim 50 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 20 (+5) | 14 (+2) | 17 (+3) | 2 (–4) | 12 (+1) | 5 (–3) |
Saving Throws Dex +5, Con +6, Wis +4
Skills Stealth +5, Perception +4
Senses darkvision 60 ft., passive Perception 14
Languages —
Challenge 6 (2,300 XP)
Traits
- Amphibious. Eogyrinus can breathe air and water.
- Swamp Camouflage. Advantage on Dex (Stealth) checks in aquatic or swampy terrain.
- Surprise Ambusher. If Eogyrinus surprises a creature and hits it on its first turn, the attack deals an extra 14 (4d6) damage.
Actions
- Multiattack. It makes two attacks: one with its Bite and one with its Tail Sweep.
- Bite. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 21 (3d10+5) piercing damage.
- Tail Sweep. Melee Weapon Attack: +8 to hit, reach 15 ft., one target. Hit: 17 (2d12+4) bludgeoning damage, and the target must succeed on a DC 16 Str save or be knocked prone.
- Suction Jet (Recharge 5–6). Eogyrinus expels a powerful jet of water in a 20-ft line: each creature must make a DC 16 Str save, taking 22 (4d10) bludgeoning damage and being pulled up to 15 ft toward the beast on a failed save, or half as much and no movement on a success.
Reactions
- Skull Deflection. When a creature Eogyrinus can see hits it with a melee attack while it’s in water, Eogyrinus twists its broad skull to impose disadvantage on that attack.
Tactics
- Ambush Setup: Hides beneath roots and detritus, using Swamp Camouflage to remain undetected.
- Opening Strike: Initiates combat with Suction Jet to isolate a target, then follows with Multiattack to maximize damage.
- Hit-and-Retreat: Uses superior swim speed to dart among cover, avoiding entanglement and resetting its ambush.
- Defensive Twist: When pressured in melee, relies on Skull Deflection to frustrate attackers and slip away.
This amphibian is the size of a large crocodile, with a long, slender body and short legs. Its crocodilian head bears a maw filled with sharp teeth.
Originally Posted by Shade of the En World forums.
On this Thread
Eogyrinus is a powerful swimmer that moves quickly through the water. A predator, lying in wait in the shadows, better hunting in the water, Eogyrinus will make a grab for prey passing close by on land.
An eogyrinus is about 15 feet long and weighs close to 1,000 pounds.
| Eogyrinus | |
| Large animal (Aquatic) | |
| Hit Dice | 4d8+28 (46 hp) |
| Initiative | +1 |
| Speed | 5 ft. (1 square), Swim 30 ft. |
| Armor Class | 12 (-1 size, +1 Dexterity, +2 natural), touch 10, flat-footed 11 |
| Base Attack/Grapple | +3/+13 |
| Attack | Bite +9 melee (1d8+9) |
| Full Attack | Bite +9 melee (1d8+9) |
| Space/Reach | 10 ft./5 ft. |
| Special Attacks | Death roll, improved grab |
| Special Qualities | Amphibious, Low-Light Vision |
| Saves | Fort +11, Ref +5, Will +1 |
| Abilities | Strength 23, Dexterity 12, Constitution 25, Intelligence 1, Wisdom 11, Charisma 5 |
| Skills | Hide +3*, Listen +3, Move Silently +3, Spot +4, Swim +17 |
| Feats | Stealthy, Weapon Focus (bite) |
| Environment | Warm forests and marshes |
| Organization | Solitary or pod (2-12) |
| Challenge Rating | 3 |
| Treasure | None |
| Alignment | Always neutral |
| Advancement | 5-6 HD (Large); 7-14 HD (Huge) |
| Level Adjustment | – |
COMBAT
Eogyrinus hunt prey much like crocodiles, hiding the bulk of its body underwater, with only its eyes and nostrils breaking the surface. It grabs prey that approaches the water, drags it under, and attempts to rip it apart with its death roll.
Death Roll (Ex): An eogyrinus that successfully gets a hold on an opponent with its improved grab ability lodges its prey against natural terrain or even another eogyrinus, then bites down hard and twists its body to tear off large pieces of meat. If another eogyrinus joins the grapple, both eogyrinuses deal maximum damage. This attack deals bite damage each round until the victim breaks free, the eogyrinus is slain, or the victim dies.
Improved Grab (Ex): To use this ability, an eogyrinus must hit an opponent of up to one size smaller with its bite attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can use its death roll in the following round.
Skills: An eogyrinus has a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.
*An eogyrinus gains a +4 racial bonus on Hide checks when in the water. Further, an eogyrinus can lie in the water with only its eyes and nostrils showing, gaining a +10 cover bonus on Hide checks.
Originally apperead in Dragon Magazine #176 (1991).