It’s neither a fungus nor an animal. The Acid Sludge Creeper is a semi-sentient colony of digestive microorganisms that have found a home in pools of alchemical effluent and forgotten magical sewers. This gelatinous, translucent mass, about the size of a large dog, moves with hypnotic slowness, its body emitting a dull, greenish glow that dimly illuminates the dark corridors.

Its advance is silent, except for the soft, damp sound of its body dragging across the stone. An aura of acidic moisture and a pungent, metallic smell precedes it. It does not hunt out of predatory instinct, but out of a primal desire for “feeding”: it is inexorably drawn to the warmth of torches and lamps, and the cold, tempting smell of metal. To the Creeper, a gleaming sword or armor of steel is a sumptuous delicacy. When it finds its “food,” it does not attack with fury, but simply envelops the object, and a sharp hiss and the smell of burning metal fill the air as corrosion does its work.

Applications in Adventures

Guardian of Corrosive Treasure:  The adventurers’ treasure is in a room with several puddles on the floor. Inside each puddle, a Creeper slumbers. Players will need to use creativity (hooks, illusions, creating distractions with heat) to retrieve the items without damaging their equipment.

The Corridor Challenge:  A narrow, damp corridor is the territory of a Creeper. It doesn’t attack the characters directly, but blocks the passage. Attacking it up close means risking weapons and armor. They will need to find a way around it, kill it from a distance (which may make noise and attract other threats), or sacrifice a metal item to distract it.

The Blacksmith’s Problem:  A village blacksmith is desperate. His water source has been infected by one or more Creepers, and his tools and metal stock have begun to dissolve. The adventurers are hired to descend to the source and clean up the contamination.

Solution to a Bigger Problem:  The adventurers find a locked chest made of extremely resistant metal, or a door with incredibly stiff hinges. Finding and “recruiting” a Creeper (using an iron bar as bait) may be the key to opening them, of course, at the risk of damaging the contents in the process.

Source of Alchemical Reagent:  An eccentric alchemist will pay handsomely for the intact “stabilizing core” of a Creeper. This transforms combat from a mere struggle for survival into a mission of precision: how to kill the creature without using methods that destroy its precious core?

Creature’s Abilities

  • Metal Corrosion:  Any metal weapon that hits the Crawler suffers a permanent -1 damage penalty. Metal armor on those hit loses a permanent -1 AC penalty. Items are destroyed if they reach 0 damage.
  • Resistance to Cuts/Pierces:  Reduces damage from cut and pierce weapons by half.
  • Vulnerability to Fire:  Takes +50% fire damage.
  • Immunities:  Immune to poison and mental effects (enchantment, illusion).

Properties by System

For OSE (Old School Essentials)

AC 13 [6], DV 3** (13 HP), Attack 1 × touch (1d6), THAC0 17 [+2], Move 6 (20′), Save V12 P13 M14 S15 F16 (N1), Mor 8, Ali Neutral, XP 50, No/Encounter 1d3

For DCC (Dungeon Crawl Classics)

Init -2, AC 12, Pseudopod Attack +1 (1d6), HD 3d10, Act 1d20, Mor 7, Ali Neutral

For Old Dragon 2

ND 3, PV 18, CA 14, FOR 14 (+2), DES 6 (-2), CON 16 (+3), INT 1 (-5), SAB 10 (0), CAR 3 (-4), Pseudopod Attacks +4 (1d6+2), Treasure Core (50 PO)