5e SRD >Gamemastering >Monsters & Foes >Monsters By Type >Monstrosities >


Large monstrosity, neutral

Armor Class 12 (natural armor)
Hit Points 103 (9d10 + 54)
Speed 40 ft.

15 (+2) 6 (–2) 22 (+6) 10 (+0) 14 (+2) 14 (+2)

Saving Throws Constitution +9
Skills Athletics +5, Stealth +1
Damage Immunities poison
Condition Immunities paralyzed, poisoned, prone, stunned, unconscious
Senses darkvision 60 ft.
Languages Common, draconic (understands but can’t speak)
Challenge 4 (1,100 XP)

Special Traits

  • Immutable Form. The arcanoplasm is immune to any spell or effect that would alter its form.
  • Absorb Arcane Energy. Any arcane spell targeted at an arcanoplasm is automatically absorbed into its body. This cures 1 point of damage per 3 points of damage the spell would otherwise deal; nondamaging spells cure 1 point of damage per spell slot level used. Spells that affect an area are not absorbed, but neither do they affect the arcanoplasm. The arcanoplasm can’t absorb magic from spells that it cast itself using arcane spell mimicry, and it can’t absorb divine magic, which affects it normally.
  • Amorphous. An arcanoplasm can move through gaps as small as 1 square inch without squeezing.
  • Arcanesense. An arcanoplasm can automatically detect the location of any arcane spellcaster within 100 feet. This ability is not blocked by any material.
  • Arcane Spell Mimicry. As an action, an arcanoplasm can mimic any arcane spell of 4th level or lower cast within 30 feet of it on its next turn. The arcanoplasm has a DC 14 spell save and +6 to hit with spell attacks and requires no components. Because of its innately magical nature, an arcanoplasm adds both its Constitution and Charisma modifiers to concentration checks when it takes damage.


  • Multiattack. The arcanoplasm makes one Slam attack and one Constriction attack.
  • Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 5 (1d6 + 2) bludgeoning damage plus 3 (1d6) acid damage, and the target is grappled (escape DC 16).
  • Constriction. One creature already grappled by the arcanoplasm is crushed for 5 (1d6 + 2) bludgeoning damage plus 7 (2d6) acid damage.
Thought to be the result of a failed magic experiment, wizards and sorcerers alike have tried for years to gather information on this alien creature, but thus far such information has eluded even the most resourceful of casters. Arcanoplasms are found in areas where the residual energies of arcane magic linger. Such areas include ruined wizard towers, keeps, dungeons, and so forth. Here they feed and remain until disturbed. Most encounters with these monsters are take place in such locations as the arcanoplasm rarely travels far from its lair. And since it lairs in ruins and other such adventurer-attracting places, it rarely has to wait long between meals.
Section 15: Copyright Notice

City of Brass ©2018 Frog God Games; Authors: Casey Christofferson and Scott Greene