Giant Amoeba — The Living Mud
At a Glance
Giant Amoeba — a deceptively small but dangerous living mass of protoplasm
Mindless aquatic ooze; an instinctive hunter without malice or allegiance
Small; its relative size makes it easy to overlook amid mud and standing water
Flooded tunnels, stagnant pools, damp crypts, peat bogs and cisterns
It can seize small prey, draw a victim into its body and digest living tissue
Unlike a black pudding, its weak acid does not eat through metal or stone
The stable boy’s bucket comes out of the cistern alive. What looked like a sheet of muddy water pours across its rim, closes around his wrist and begins to draw him back towards the well. There is no mouth, no scream and no thought behind it—only a membrane full of digestive fluid and a dark nucleus pulling slowly towards warmth.
Behavior:
The Giant Amoeba is a slow-moving but relentless predator. It lacks intelligence, following movement and the scent of organic matter rather than attacking metal or stone. It is largely blind, relying on vibration and chemical cues to detect movement. When threatened or hungry, it becomes aggressive, stretching its amorphous form to envelop prey and dissolve it with potent acidic secretions.
Habitat:
Found primarily in murky swamps, fetid bogs, and deep underground caverns filled with stagnant water, the Giant Amoeba thrives in places where light barely penetrates and decay is abundant. It favors environments rich in organic debris, where it can easily ambush unsuspecting creatures.
Modus Operandi:
The Giant Amoeba lies in wait, nearly invisible amidst the muck, until it senses vibrations nearby. It then slowly oozes toward its target, engulfing it in a suffocating embrace of slime. Once trapped inside, victims are broken down by acidic enzymes, their flesh liquefied and absorbed. A starving amoeba may shed tiny new bodies that eventually form a swarm, but sword blows do not split it into new combatants.
Motivation:
Driven solely by hunger and survival, the Giant Amoeba has no goals beyond consuming nutrients to sustain and grow. Its existence is one of primal consumption—an unstoppable force of nature, indifferent to all else but the next meal.
Game Statistics
Giant Amoeba
Small Ooze, Unaligned
AC 8; Initiative −5 (5); HP 27 (5d6 + 10); Speed 10 ft., Climb 10 ft., Swim 20 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 12 (+1) | 1 (−5) | 14 (+2) | 1 (−5) | 6 (−2) | 1 (−5) |
Saving Throws Str +1, Dex −5, Con +2, Int −5, Wis −2, Cha −5
Immunities Acid, Poison; Charmed, Deafened, Exhaustion, Frightened, Prone
Senses Blindsight 30 ft., Passive Perception 8; Languages None
CR 1/2 (100 XP; PB +2) — original conversion
Traits
Amorphous. The amoeba can squeeze through openings as narrow as 1 inch without extra movement.
Amphibious. It can breathe air and water.
Weak Digestive Acid. Its acid damages flesh and other organic substances but does not corrode metal or stone. The amoeba cannot split when hit by a weapon.
Actions
Pseudopod. Melee Attack Roll: +3, reach 5 ft., one target. Hit: 4 (1d6 + 1) Bludgeoning damage plus 3 (1d6) Acid damage. If the target is Medium or smaller, it must succeed on a DC 11 Strength saving throw or have the Grappled condition (escape DC 11). The amoeba can grapple only one creature at a time.
Envelop. One Small or Tiny creature grappled by the amoeba makes a DC 11 Strength saving throw. On a failure it becomes engulfed, Blinded and Restrained, moves with the amoeba and takes 7 (2d6) Acid damage at the start of each of the amoeba’s turns. It can use an action to make a DC 11 Strength (Athletics) check to escape into an empty adjacent space. The amoeba releases the creature if it dies.
Bonus Actions
Digest. One creature grappled or enveloped by the amoeba takes 3 (1d6) Acid damage.
Giant Amoeba
Small ooze, unaligned
Armor Class 8; Hit Points 39 (6d6 + 18); Speed 10 ft., climb 10 ft., swim 20 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 12 (+1) | 6 (−2) | 16 (+3) | 1 (−5) | 7 (−2) | 2 (−4) |
Skills Stealth +2; Damage Immunities acid, poison
Condition Immunities blinded, charmed, deafened, exhaustion, frightened, prone
Senses blindsight 30 ft. (blind beyond this radius), passive Perception 8; Languages —; Challenge 1/2 (100 XP) — original conversion
Traits
Amorphous. The amoeba can move through a gap at least 1 inch wide without squeezing.
Amphibious. It can breathe air and water.
Weak Acid. Its digestive fluid damages organic matter but does not dissolve metal or stone. This creature does not inherit the black pudding’s Split ability.
Actions
Pseudopod. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning plus 7 (2d6) acid damage. A Medium or smaller target is grappled (escape DC 11); while holding a target the amoeba cannot grapple another.
Envelop. If the amoeba is grappling a Small or Tiny creature, it can draw that creature into its body. The target must succeed on a DC 11 Strength saving throw or become blinded and restrained while enveloped. It moves with the amoeba and takes 7 (2d6) acid damage at the start of the amoeba’s turns. It can escape by using an action to succeed on a DC 11 Strength check, exiting into an empty adjacent space.
Giant Amoeba — CR 1
XP 400; N Small ooze (aquatic); Init −5; Senses blindsight 30 ft.; Perception −5
DEFENSE
AC 6, touch 6, flat-footed 6 (−5 Dex, +1 size); hp 15 (2d8 + 6)
Fort +3, Ref −5, Will −5
Defensive Abilities ooze traits
OFFENSE
Speed 10 ft., climb 10 ft., swim 20 ft.; Space/Reach 5 ft./5 ft.
Melee slam +3 (1d3+1 plus 1d3 acid and grab)
Special Attacks constrict (1d3+1 plus 1d3 acid)
STATISTICS
Str 12, Dex 1, Con 16, Int —, Wis 1, Cha 1
Base Atk +1; CMB +1 (+5 grapple); CMD 6 (can’t be tripped)
Skills Climb +9, Swim +9 (racial +8 to both); Feats —; SQ amphibious
ECOLOGY
Environment land or underground; Organization solitary or colony (2–9); Treasure none
SPECIAL ABILITIES
Grab (Ex). On a slam hit, the amoeba can attempt to start a grapple with the listed CMB bonus.
Constrict (Ex). When it successfully maintains a grapple, it deals the listed constrict and acid damage.
Amphibious (Ex). It breathes both air and water. It cannot corrode metal like a black pudding, and it has no weapon-triggered split.
Giant Amoeba
N Small Ooze (Aquatic); Challenge Rating 1 — original 3.5e conversion
Hit Dice 2d10+6 (17 hp); Initiative −5; Speed 10 ft., climb 10 ft., swim 20 ft.
Armor Class 6 (+1 size, −5 Dex), touch 6, flat-footed 6
Base Attack/Grapple +1/−2; Attack slam +3 melee (1d3+1 bludgeoning plus 1d3 acid); Full Attack slam +3 melee (1d3+1 plus 1d3 acid)
Space/Reach 5 ft./5 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 12 (+1) | 1 (−5) | 16 (+3) | — | 1 (−5) | 1 (−5) |
Special Attacks constrict (1d3+1 plus 1d3 acid), improved grab
Special Qualities blindsight 30 ft., amphibious, ooze traits, immune to mind-affecting effects
Saves Fort +3, Ref −5, Will −5; Skills Climb +9, Swim +9; Feats —
Environment land or underground; Organization solitary or colony (2–9); Treasure none; Alignment always neutral
COMBAT
Improved Grab (Ex). A slam hit can start a grapple against a smaller opponent without provoking an attack of opportunity. The amoeba may constrict on a successful grapple check.
Constrict (Ex). A successful grapple check deals the listed slam and acid damage.
Amphibious (Ex). Breathes air and water. Its weak acid digests organic tissue and does not corrode metal or stone. Slashing and piercing weapons do not trigger splitting.
Skills. The amoeba’s racial bonuses are +8 on Climb and Swim checks, and it can take 10 even when threatened.
What Is Happening Right Now?
The Water That Moves Uphill
In an abandoned millrace, muddy water climbs the stones against the current. A miller’s child is trapped beyond the sluice, where several amoebas crawl through the wet masonry. The characters can divert the flow, cross on iron grating, or enter the flooded channel to reach the child. The danger is suffocation and digestive acid, not dissolving armour.
Something in the Horse Trough
Animals at a roadside stable refuse to drink. The water looks clear until a groom dips his hand and it catches against a nearly transparent membrane. More amoebas wait in a nearby cistern, and a delivery of fresh water is due before nightfall. The party must drain the cistern safely and learn how the creatures reached it.
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