5e SRD >Creatures >

Carapace Symbiont

Medium ooze, chaotic natural

Armor Class 17 (natural)
Hit Points 157 (15d8 + 90)
Speed 15 ft.

13 (+1) 8 (–1) 22 (+6) 15 (+2) 11 (+0) 10 (+0)

Saving Throws Dex +3, Con +10
Skills Deception +4, Persuasion +4, Stealth +3
Damage Vulnerabilities slashing damage from magical attacks (varies: see text)
Damage Immunities acid, cold, fire, force, lightning, poison, radiant; piercing damage from nonmagical attacks
Condition Immunities blindness, paralysis, poison, stunned (varies: see text)
Damage Resistances bludgeoning and piercing damage (varies: see text)
Senses darkvision 60 ft., passive Perception 10
Languages Common, Deep Speech, Undercommon, telepathy (touch)
Challenge 11 (7,200 XP)


  • Defensive Symbiosis. A carapace symbiont can enter into a symbiotic union with a Small, Medium, or Large creature. The creature must be sapient and language-capable. If the symbiotic partner agrees, the carapace symbiont surrounds the creature’s body with its own and hardens there as a suit of nigh-indestructible armor. This armor requires no proficiencies but otherwise counts as light armor. It weighs 40 pounds (even for small or large creatures). It offers an armor class of 13 with no Dexterity modifier maximum and no Stealth disadvantage. In addition, many of the armor’s immunities offer resistances to the target of the symbiotic union. The immunities that can be offered as resistances to the “wearer” are: acid, cold, fire, force, lightning, and radiant damage, as well as piercing and slashing damage from nonmagical attacks. The carapace symbiont can offer resistances to damage types only if it has immunity to those damage types. While in Defensive Symbiosis with a wearer, the carapace symbiont always shares that wearer’s initiative.
  • Fatal Flaw. Every carapace symbiont is cursed with a fatal flaw. One of the damage types to which it should be immune is always instead a vulnerability (some carapace symbionts might have more than one fatal flaw if the curse hit them especially hard). Determine which damage type is the fatal flaw by rolling 1d8 and comparing the result to the list in the Defensive Symbiosis description above. If the result matches with acid, cold, fire, force, lightning, or radiant damage, the symbiont is vulnerable to that type of damage instead of immune. If the result is slashing or piercing damage, the symbiont is vulnerable to that type of damage from magical weapons and not resistant to that type of damage even from nonmagical attacks. The carapace symbiont stats above reflect a symbiont whose fatal flaw is slashing damage. A symbiont with a fire or acid fatal flaw would be as resistant to slashing damage as this one is to piercing damage.
  • Innate Spellcasting. The carapace symbiont’s spellcasting ability is Intelligence (spell save DC 16, +8 spell attack bonus). The carapace symbiont can innately cast the following spells, requiring no components:
  • Oozing Dodge. A carapace symbiont may use its reaction to yank itself out of the way of an oncoming attack. After the attack is rolled, but before damage is done, the symbiont may partially adopt goo form in order to avoid taking damage along with the symbiotic partner with a successful DC 16 Dexterity saving throw; however, if it uses this ability (even if it fails to dodge the attack), its “wearer” loses all its armor benefits for 1d2 rounds as it rehardens itself properly.
  • Symbiosis Dependence. A carapace symbiont must eat food like any living thing, but it is, in addition, dependent upon a telepathic link to a sapient, language-capable creature in order to maintain consciousness and free will. A carapace symbiont that goes more than one week without a symbiotic link loses one point of Intelligence per week. This Intelligence can be recovered only through symbiosis. If a carapace symbiont reaches 0 intelligence, it curls into a small gray ball and hardens into torpor. It does not require food (or anything else) while in torpor, but it cannot move, think, speak, or take any action until it is touched again by a sapient and language-capable creature.
  • Varying Ability. A carapace symbiont cannot move or take attack actions while hardened in symbiosis with another being. If a carapace symbiont is in its armor state, it is capable only of the following: using Oozing Dodge, reverting to its liquid state, and communicating telepathically with its wearer. While in its formless, liquid state, the carapace symbiont can also move in an oozing puddle, attack as described in the stat block, cast spells, manipulate objects, eat, speak, and do anything else of which a puddle of sapient, mobile goo is capable.


  • Form Shift. As an action, a carapace symbiont may adopt its goo form at any time. Adopting its armor form requires three rounds.
  • Slap. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 18 (2d12 + 5) slashing damage.


A carapace symbiont resembles a glob of goo that shifts its colors as it moves, shimmering through a variety of hues. An psychic race of evil overseers created carapace symbionts to serve as a more comfortable suit of armor, and, in a pinch, a psychic snack. Over the generations, however, the symbionts learned to communicate silently with one another and eventually rebelled. As they fled, their former masters cursed them, marring their previous near invulnerability such that each of them has a fatal flaw.

This seemed a slight enough price to pay for freedom, until the symbionts realized they could not sustain one another psychically and still needed union with other beings to remain conscious. Given what they had endured, this prospect did not appeal to them, and to this day most have difficulty trusting in bonds formed with other creatures. Honesty and friendship are difficult for them, and most are liars. When in danger (such as standing between a “wearer” and an attack to which they are not immune), they are likely to betray any agreements they have made and save themselves, sometimes going so far as to plane-shift away, leaving the “wearer” undefended in the middle of a battle.

Though a swirling, marbled gray while in torpor, a goo-form carapace symbiont shifts colors in beautiful whorls and shimmers constantly as it moves. When it takes armor form, a carapace symbiont can choose which color to assume and whether to adopt a metallic sheen, but it cannot shift colors again without reverting to goo form. Carapace symbionts eat plant matter (regardless of its food value to humanoids) and minerals (sometimes precious ones). They dislike meat and other animal products. When forming an agreement with a symbiotic companion, many ask to be fed and/or paid for their time. If they are paid, they eat the money.

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Tome of Horrors 2020, (C) 2020, Necromancer Games