Acanthostega

Small beast, unaligned

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Armor Class 12 (natural armor)
Hit Points 22 (4d8 + 4)
Speed 10 ft., swim 30 ft.

STR	DEX	CON	INT	WIS	CHA
11 (+0)	14 (+2)	12 (+1)	1 (−5)	12 (+1)	6 (−2)

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Skills Perception +3, Stealth +4 (in water)
Senses darkvision 30 ft., passive Perception 13
Languages —
Challenge 1/4 (50 XP)
Proficiency Bonus +2

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Amphibious

The acanthostega can breathe both air and water.

Aquatic Stealth

While submerged in murky water or thick vegetation, the acanthostega has advantage on Dexterity (Stealth) checks to hide.

Primitive Limbs

The acanthostega’s limbs are poorly suited to land. If it moves more than 10 feet on solid ground during its turn, its speed is halved until the end of that turn.

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Actions

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target.
Hit: 7 (2d4 + 2) piercing damage.

Ambush Lunge (Recharge 5–6). If the acanthostega begins its turn hidden and within 20 feet of a creature in water, it can swim up to its speed and make a Bite attack with advantage. On a hit, the target takes an extra 4 (1d8) piercing damage.

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Tactics

An acanthostega lies in wait among reeds and submerged logs, relying on stillness and camouflage until prey drifts too close. It strikes in a sudden burst, clamping down with its jaws before retreating into deeper water. On land it is slow and vulnerable, preferring to slip away rather than fight. Druids and sages regard it as a living relic of ancient ages, when the first beasts began to crawl from the sea to the shore.

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“Few expect danger from the shallows—until the water ripples, and the swamp’s ancient jaws strike.”

Acanthostega

Small animal, CR 1/3

This relic of the Devonian drifts silently in shallow waters, its many-fingered limbs paddling with eerie precision as it waits for prey to wander too close. Few adventurers expect danger from the shallows, yet its bite can be surprisingly vicious.

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XP 135
N Small animal
Init +2; Senses darkvision 30 ft., low-light vision, scent; Perception +5

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DEFENSE

AC 13, touch 13, flat-footed 11 (+2 Dex, +1 size)
hp 7 (1d8+3)
Fort +5, Ref +4, Will +1

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OFFENSE

Speed 10 ft., swim 30 ft.
Melee bite +2 (1d6+1)
Special Attacks ambush lunge (Ex)

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STATISTICS

Str 13, Dex 15, Con 14, Int 1, Wis 12, Cha 6
Base Atk +0; CMB +0; CMD 11
Feats Weapon Finesse
Skills Perception +5, Stealth +6 (+10 in water), Swim +9
SQ amphibious (Ex), primitive limbs (Ex)

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ECOLOGY

Environment warm swamps, marshes, and shallow rivers
Organization solitary, pair, or clutch (3–6)
Treasure none

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SPECIAL ABILITIES

Amphibious (Ex). An acanthostega can breathe both air and water.

Primitive Limbs (Ex). Its paddle-like legs are poorly suited to land. If it moves more than 10 feet on solid ground in a single round, it becomes staggered until the start of its next turn.

Ambush Lunge (Ex). If the acanthostega begins its turn hidden in water and charges a target within 20 feet, it gains a +4 bonus on its first attack roll that round. On a successful bite, it deals an extra 1d6 points of piercing damage.

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COMBAT

Before Combat. The acanthostega hides in reeds, mud, or submerged logs, often near the water’s edge, waiting for small prey.

During Combat. It strikes quickly using Ambush Lunge, targeting the smallest or weakest creature in range. After attacking, it retreats back into deeper water if possible.

Morale. On land, the acanthostega flees immediately if seriously injured. In water, it fights until reduced to 2 hp or less, then attempts to escape into deeper pools.

Acanthostega

Small Animal, Unaligned

This relic of the Devonian drifts silently through shallow waters, its many-fingered paddle-like limbs propelling it with eerie stealth. Few adventurers expect danger from the shallows, yet its sudden bite can be surprisingly vicious.

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Hit Dice: 1d8+1 (5 hp)
Initiative: +2
Speed: 10 ft., swim 30 ft.
Armor Class: 13 (+2 Dex, +1 size), touch 12, flat-footed 11
Base Attack/Grapple: +0 / -1
Attack / Full Attack: Bite +2 melee (1d4+1)
Space / Reach: 5 ft. / 5 ft.
Saves: Fort +3, Ref +4, Will +0
Abilities: Str 12, Dex 15, Con 12, Int 1, Wis 12, Cha 6
Skills: Perception +3, Hide +8 (+12 in water), Swim +7
Feats: Weapon Finesse

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Special Qualities and Abilities

The acanthostega is amphibious, able to breathe both air and water. Its primitive paddle-like limbs make movement on land awkward; if it moves more than 10 feet in a round on solid ground, it becomes staggered until the start of its next turn. While hidden in water, the creature can use Ambush Lunge to strike suddenly at a target within 20 feet, gaining +4 to its first attack roll and dealing an extra 1d6 piercing damage. It has low-light vision for hunting in murky waters.

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Combat Tactics

The acanthostega waits patiently in reeds, mud, or submerged logs, striking opportunistically at the smallest or most isolated prey. It relies on surprise and its ambush attack to inflict damage quickly, then retreats to deeper water. On land it avoids combat whenever possible and flees if seriously injured.

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Ecology

Small and elusive, acanthostegas inhabit warm swamps, marshes, and shallow rivers, often alone, in pairs, or in clutches of three to six. They leave no treasure behind, acting purely as ancient predators of their watery ecosystems.

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Optional Lair Action (Swamp Ambush)

In a primeval swamp lair, an acanthostega can stir mud in a 10-ft.-radius area once per round. Non-swimming creatures in this area take a –2 penalty on Spot checks and Reflex saves until the start of the acanthostega’s next turn.