Koolasuchus

Huge Beast (Unaligned), Challenge 7 (2,900 XP)

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Armor Class 16 (natural armor)
Hit Points 147 (14d12 + 56)
Speed 30 ft., swim 50 ft.

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STR	DEX	CON	INT	WIS	CHA
21 (+5)	12 (+1)	18 (+4)	2 (–4)	14 (+2)	5 (–3)

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Saving Throws Con +7, Wis +5
Skills Perception +5, Stealth +5
Senses darkvision 60 ft., tremorsense 30 ft., passive Perception 15
Languages —
Proficiency Bonus +3

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Traits

Amphibious.
The Koolasuchus can breathe both air and water.

Natural Camouflage.
While motionless and submerged or lying in mud, the Koolasuchus has advantage on Dexterity (Stealth) checks to hide.

Hold Still.
If the Koolasuchus hasn’t moved since the end of its last turn, it gains resistance to bludgeoning and piercing damage until it moves again.

Tremor Predator.
The Koolasuchus can sense the location of any creature in contact with the same body of water or surface within 30 feet, even if it is blinded or deafened.

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Actions

Multiattack.
The Koolasuchus makes two attacks: one with its Bite and one with its Tail Slam.

Bite. Melee Weapon Attack: +8 to hit, reach 10 ft., one target.
Hit: 22 (3d10 + 5) piercing damage. If the target is Medium or smaller, it must succeed on a DC 16 Strength saving throw or be grappled (escape DC 16) and restrained until the grapple ends. The Koolasuchus can grapple only one creature at a time.

Tail Slam. Melee Weapon Attack: +8 to hit, reach 10 ft., one target.
Hit: 18 (3d8 + 5) bludgeoning damage. If the target is Large or smaller, it must succeed on a DC 16 Strength saving throw or be knocked prone.

Death Roll (Recharge 5–6).
The Koolasuchus violently twists its body while grappling a creature. The grappled target must make a DC 16 Constitution saving throw, taking 33 (6d10) bludgeoning damage on a failed save, or half as much on a success. If the creature is in water, it is dragged beneath the surface. If already submerged, the target begins to drown unless it can breathe underwater.

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Tactics

The Koolasuchus is an ambush predator that prefers to strike from concealment beneath riverbanks or muddy shallows. It targets isolated or distracted prey and drags them into deep water. It fights with explosive bursts of violence, using Death Roll to finish off grappled targets quickly. If seriously injured, it retreats into deep or murky water to escape, reemerging only when the threat has passed or weakened.

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Environmental Signs

Rivers or lakes inhabited by a Koolasuchus may show signs such as:

• Missing livestock or travelers near fords and crossings
• Bones and broken debris washed up on shorelines
• Murky water with no clear cause
• Unnatural silence, as wildlife avoids the area entirely

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Optional Regional Effect
While the Koolasuchus remains in its lair, the surrounding river becomes unnaturally still and silent. Wisdom (Survival) checks made to detect aquatic predators in the area have disadvantage.

Koolasuchus

CR 7
XP 3,200
N Huge animal
Init +2; Senses darkvision 60 ft., low-light vision, tremorsense 30 ft.; Perception +13

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DEFENSE

AC 20, touch 10, flat-footed 18 (+2 Dex, +10 natural, –2 size)
hp 105 (10d8+60)
Fort +11, Ref +9, Will +5
DR 5/piercing (see Hold Still); Resist cold 10 (see Cold-Blooded)
CMD 29 (33 vs. trip)

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OFFENSE

Speed 30 ft., swim 60 ft.
Melee bite +15 (2d8+10 plus grab), tail slap +13 (2d6+6)
Space 15 ft.; Reach 10 ft.

Special Attacks constrict (2d8+10), death roll, grab, powerful charge

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STATISTICS

Str 31, Dex 15, Con 23, Int 1, Wis 16, Cha 5
Base Atk +7; CMB +19 (+23 grapple); CMD 31
Feats Improved Natural Attack (bite), Power Attack, Toughness, Lightning Reflexes, Skill Focus (Stealth)
Skills Perception +13, Stealth +6 (+10 in water or mud), Swim +20
SQ amphibious, hold still, natural camouflage

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ECOLOGY

Environment cold rivers, alpine lakes, glacial valleys
Organization solitary
Treasure none

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SPECIAL ABILITIES

Amphibious (Ex)
The Koolasuchus can breathe both air and water.

Constrict (Ex)
The Koolasuchus deals 2d8+10 bludgeoning damage when it successfully maintains a grapple.

Death Roll (Ex)
As a full-round action, the Koolasuchus can violently spin while grappling a creature. The grappled target must succeed on a DC 21 Fortitude save or take 4d8+15 bludgeoning damage and become pinned. A successful save halves the damage and negates the pin. If the target is in water and fails the save, it also begins to drown unless it can breathe water. The save DC is Strength-based.

Grab (Ex)
If the Koolasuchus hits with its bite, it can attempt to start a grapple as a free action without provoking an attack of opportunity.

Hold Still (Ex)
If the Koolasuchus does not move for 1 full round, it gains damage reduction 5/piercing and cold resistance 10 until it moves again.

Natural Camouflage (Ex)
When lying motionless in natural water or muddy terrain, the Koolasuchus gains a +4 racial bonus on Stealth checks.

Powerful Charge (Ex)
When the Koolasuchus charges while submerged, it gains a +2 bonus on its attack roll and deals double tail slap damage.

Tremorsense (Ex)
The Koolasuchus can sense the location of anything in contact with the same body of water or surface within 30 feet.

Cold-Blooded (Ex)
The Koolasuchus has cold resistance 10 but suffers a –2 penalty on attack rolls, saves, and skill checks in hot or arid environments.

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DESCRIPTION

The Koolasuchus is a colossal, amphibious predator—an ancient remnant of a bygone age. With a broad, flattened skull and a barrel-shaped body cloaked in slime and sediment, it lies buried beneath riverbeds and icy lakes, waiting motionless for vibrations in the water to betray nearby prey. When it strikes, it does so with explosive power, crushing and drowning its victims in a flurry of thrashing violence.

Koolasuchus thrives in cold, slow-moving rivers and glacial waterways, where its sluggish metabolism and ambush tactics offer the greatest advantage. Though mindless and territorial, it displays a primal cunning: avoiding confrontation when injured and stalking wounded prey with disturbing persistence.

Koolasuchus

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Huge Animal
Hit Dice: 10d8+50 (95 hp)
Initiative: +2
Speed: 30 ft. (6 squares), swim 60 ft.
Armor Class: 20 (–2 size, +2 Dex, +10 natural), touch 10, flat-footed 18
Base Attack/Grapple: +7/+25
Attack: Bite +15 melee (2d8+12)
Full Attack: Bite +15 melee (2d8+12) and tail slap +10 melee (2d6+6)

Space/Reach: 15 ft./10 ft.
Special Attacks: Constrict (2d8+12), death roll, improved grab, powerful charge
Special Qualities: Amphibious, cold resistance 10, hold still, low-light vision, natural camouflage, tremorsense 30 ft.
Saves: Fort +12, Ref +9, Will +5
Abilities: Str 35, Dex 15, Con 21, Int 1, Wis 14, Cha 6
Skills: Hide +0*, Listen +8, Spot +8, Swim +20
Feats: Improved Natural Attack (bite), Power Attack, Toughness, Lightning Reflexes, Skill Focus (Hide)

Environment: Cold rivers, marshes, and glacial lakes
Organization: Solitary
Challenge Rating: 7
Treasure: None
Alignment: Always neutral
Advancement: 11–15 HD (Huge); 16–20 HD (Gargantuan)
Level Adjustment: —

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Combat

Koolasuchus is a stealthy ambush predator that uses its powerful jaws and overwhelming strength to drag prey into the water. It prefers cold, slow-moving rivers where it can lie motionless for hours, waiting to strike with lethal precision.

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Amphibious (Ex):
The Koolasuchus can breathe both air and water.

Constrict (Ex):
A Koolasuchus deals 2d8+12 points of bludgeoning damage with a successful grapple check when using its bite.

Death Roll (Ex):
As a standard action while grappling a creature in water, the Koolasuchus can spin violently to crush and drown its foe. The grappled target must succeed on a DC 24 Fortitude save or take 4d8+18 bludgeoning damage and become pinned. A successful save halves the damage and negates the pin. Creatures that breathe air and are fully submerged must begin holding their breath or begin to drown. The save DC is Strength-based.

Improved Grab (Ex):
To use this ability, the Koolasuchus must hit a creature of Large size or smaller with its bite attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity.

Hold Still (Ex):
If the Koolasuchus remains motionless for 1 full round, it gains DR 5/piercing and cold resistance 10 until it moves again.

Natural Camouflage (Ex):
When in muddy water or silt-laden terrain, the Koolasuchus gains a +8 racial bonus on Hide checks.
(Already factored into skills.)

Powerful Charge (Ex):
When the Koolasuchus charges a creature while submerged, its tail slap deals double damage and gains a +2 bonus on the attack roll.

Tremorsense (Ex):
The Koolasuchus can sense the location of any creature in contact with the same body of water or soft terrain within 30 feet.

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Skills

A Koolasuchus has a +8 racial bonus on Swim checks to perform special actions or avoid hazards. It can take 10 on Swim checks even when distracted or endangered. While submerged or lying in muddy terrain, it gains a +8 bonus on Hide checks due to its natural camouflage.

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Ecology

Koolasuchus is a relic of a forgotten era, a colossal amphibian with a monstrous, flattened head and crushing jaws. Measuring over 30 feet long, it hides beneath glacial silt or slow-moving riverbeds, striking with sudden violence when prey ventures too close. Though its metabolism is slow, its burst speed and strength are formidable.

Primitive cultures living near frozen rivers often speak of the “slumbering river god” that drowns livestock or lone hunters. In truth, Koolasuchus is neither divine nor malevolent—it is an instinctive predator, cold-blooded and driven by hunger.