Copperkill Slime

Huge ooze, unaligned

Armor Class 10
Hit Points 142 (15d12 + 45)
Speed 20 ft., climb 20 ft.

18 (+4) 10 (+0) 17 (+3) 4 (–3) 8 (–1) 2 (–4)

Damage Resistances piercing, slashing
Damage Immunities acid, poison
Condition Immunities blinded, charmed, deafened, exhaustion, frightened, prone
Senses blindsight 60 ft. (blind beyond this radius), passive Perception 9
Challenge 8 (3,900 XP)
Proficiency Bonus +3


  • Amorphous. The slime can move through a space as narrow as 1 inch wide without squeezing.
  • Ooze Nature. The copperkill slime doesn’t require sleep.
  • Patinated Appearance. While the slime remains motionless, it is indistinguishable from the object or structure it is stretched across, though the object or structure appears to be covered in green paint or verdigris.
  • Spider Climb. The slime can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.


  • Multiattack. The copperkill slime makes three Pseudopod attacks. If the slime hits one creature with two Pseudopod attacks, the target is grappled (escape DC 15). Until this grapple ends, the target is restrained and takes 9 (2d8) poison damage at the start of each of its turns. The copperkill slime can have only one target grappled in this way at a time.
  • Pseudopod. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) bludgeoning damage plus 9 (2d8) poison damage.
  • Poisonous Snap (Stretched Body Only, Recharge 5–6). While the copperkill slime is covering an object or structure, it can rapidly collapse back to its normal form, ending the stretch and spraying all nearby creatures with poisonous slime. Each creature within 10 feet of any space the stretched slime occupied before collapsing must make a DC 15 Dexterity saving throw. On a failure, a creature takes 27 (6d8) poison damage and is coated in poisonous slime. On a success, a creature takes half the damage and isn’t coated in slime. A creature coated in poisonous slime takes 9 (2d8) poison damage at the start of each of its turns. A creature, including the slime-coated creature, can take an action to clean off the slime.


  • Stretch Body. The copperkill slime stretches its body across the surface of a Gargantuan or smaller object or across the surface of a wall, pillar, or similar structure no larger than a 20-foot square within 5 feet of it, sharing the space of the object or structure. The slime can end the stretch as a bonus action, occupying the nearest unoccupied space to the object or structure. The paint on the old, green wall suddenly moves and flows outward, revealing the wall underneath wasn’t green at all. Among the wealthy, one popular, though deadly, trend is that of green-painted rooms sourced from arsenic. These trends led to the creation of the first copperkill slime, an ooze formed from the poisonous paint. For curious adventurers, such a ponderous room could mean a much swifter death by ooze rather than poisoning.


Hall Guardians. Copperkill slimes are relatively docile and have enough sentience to be trained as guardians, provided their keepers maintain a steady supply of food. Ambush predators, copperkill slimes stretch themselves to adhere to walls, pillars, furniture, statues, or similar objects or support structures. As a copperkill slime stretches itself thin to hide, it tinges everything viewed through its transparent form a curious green color. When unsuspecting prey approaches the wall or object, the copperkill slime snaps back into its normal form, spraying poisonous slime on nearby creatures. This poisonous slime slowly kills the prey, and the copperkill slime devours the remains.

Section 15: Copyright Notice

Tome of Beasts 3 © 2022 Open Design LLC; Authors: Eytan Bernstein, Celeste Conowitch, Benjamin L. Eastman, Robert Fairbanks, Scott Gable, Basheer Ghouse, Richard Green, Jeremy Hochhalter, Jeff Lee, Christopher Lockey, Sarah Madsen, Ben Mcfarland, Jonathan Miley, Kelly Pawlik, Sebastian Rombach, Chelsea Steverson, Brian Suskind, Mike Welham

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