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Swarm of Silk-Gnawers - AI-generated fantasy Monster

Swarm of Silk-Gnawers

Travelers in the Glimmerwood know that when the ground starts to sparkle, it is time to run. The Silk-gnawers do not kill quickly; they weave a prison around your very soul, turning your own movement into the signal that summons their mother.

Monsters
Medium swarm · Medium · Uncommon

Swarm of Silk-Gnawers

A collective of tiny, glass-like spiders that act as a living fiber-optic network and security perimeter for a greater arachnid entity.
AC13
HP36/36
CRMedium
Init
STR
DEX
CON
INT
WIS
CHA
ConditionsNone

Combat

AC 13 · HP 36 · Medium

Swarm of Silk-Gnawers

Medium swarm (tiny beasts), unaligned
Armor Class13
Hit Points36 (8d8)
Speed
20 ft. walk,
20 ft. climb
STR
DEX
CON
INT
WIS
CHA
Saving ThrowsDexterity
SkillsStealthPerception
Damage Resistances
Bludgeoning,
Piercing,
Slashing,
Lightning
Immunities
Charmed,
Frightened,
Grappled,
Paralyzed,
Petrified,
Prone,
Restrained,
Stunned
Weaknesses
Fire
Senses
Blindsight 10 ft.,
Darkvision 60 ft.,
Passive Perception 13
Languages
None
ChallengeMedium
Initiative+3
Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny spider. The swarm can't regain hit points or gain temporary hit points.
Web Sense. While in contact with a web, the swarm knows the exact location of any other creature in contact with the same web.
Silent Alarm. The swarm is magically linked to its Matriarch. When the swarm takes damage, the Matriarch is immediately alerted to the swarm's exact location.
Conductive Field. Any creature that starts its turn in the swarm's space has its speed reduced by 10 feet. If the creature is currently under the effect of a spell that requires concentration, it must succeed on a Constitution saving throw or lose concentration as the silk disrupts the flow of mana.

Actions

Gnaw. Melee Weapon Attack: to hit, reach 0 ft., one target in the swarm's space. Hit: 7 () piercing damage, or 3 () piercing damage if the swarm has half of its hit points or fewer. The target must succeed on a Strength saving throw or be restrained by magically conductive silk (escape ). While restrained in this way, the target's speed is 0 and they have disadvantage on Dexterity saving throws.
Static Discharge (Recharge 5-6). The swarm releases a burst of stored magical energy. Each creature in the swarm's space must make a Dexterity saving throw, taking 10 () lightning damage on a failed save, or half as much damage on a successful one.

Reactions

Disperse. When the swarm is targeted by an area of effect spell that does not deal fire damage, it can use its reaction to spread out. It takes half damage from the effect, but its speed is halved until the end of its next turn.
Role
Area Denial and Debuffer
Built for
3

Notes for the game master

The swarm is intended to slow players down for a larger boss to arrive.
Movement reduction stacks with difficult terrain.

Tactics

  1. Opening

    The swarm uses Stealth to hide under leaf litter, then surges upward into the space of the most heavily armored or magically active character.

  2. Mid-fight

    Focus on using the Gnaw action to restrain targets while using Static Discharge whenever it recharges to punish those trapped within.

  3. End of the fight

    If the swarm is reduced to less than 10 hit points, it attempts to retreat back into the Matriarch's lair, leaving a trail of conductive silk to lead the Matriarch to the intruders.

  4. Retreat

    The swarm has no morale; it fights until dispersed or commanded to retreat by the Matriarch.

How it fights

Prioritize targets casting spells to utilize the Conductive Field concentration check.
Position in bottlenecks or narrow forest paths to force characters to enter the swarm's space.

Who it attacks first

Casters (to disrupt magic)
Slow-moving melee fighters (to completely stop them)
Healers

Works well with

Pairs excellently with Giant Spiders or Ettercaps who can capitalize on restrained targets.
Wisp-lights that lure players into the swarm's hiding spots.

How to beat it

Burning Hands or other cone-based fire spells will clear the swarm quickly.
Teleportation spells allow escape from the restrained condition without checks.

Ways to avoid a fight

The spiders are attracted to high concentrations of magic. A character could throw a charged magic item or spell scroll to distract the swarm.
Casting 'Speak with Animals' reveals the swarm is constantly whispering 'The Mother Sees' in a collective chittering tone.

Ecology

A shimmering, undulating carpet of thousands of tiny, translucent spiders. Their bodies are clear as quartz, and when they move, they catch the light like a rippling prism. Faint, blue sparks of static energy dance between their legs.

Behavior

They do not hunt for food, instead they gnaw on the ambient magical energy of the forest. They move with hive-mind precision, flowing over obstacles and wrapping intruders in shimmering, crackling threads.

How it lives

Silk-gnawers are a specialized evolution of the common trapdoor spider, adapted to feed on residual mana. By consuming mana, they produce a silk that is highly conductive to magical vibrations, allowing them to relay information across miles of forest floor.

Lair

They usually inhabit the Outer Thicket, the outermost defensive ring of a Matriarch's web-city.

Habitat
Enchanted forests, deep thickets, and the lairs of great spider queens.

Signs that it is near

Trees wrapped in iridescent, humming silk
Small piles of drained, ash-like insects
A faint, rhythmic clicking sound echoing through the roots
Blue static discharge when touching vegetation

Tags

swarm,
spider,
fey-wild,
conductive

Lore

Travelers in the Glimmerwood know that when the ground starts to sparkle, it is time to run. The Silk-gnawers do not kill quickly; they weave a prison around your very soul, turning your own movement into the signal that summons their mother.

What drives it

To protect the Matriarch's domain and neutralize threats through immobilization and exhaustion.

After the fight

Once the swarm is defeated, the silk begins to lose its translucency, turning into a dull, sticky gray. Somewhere deep in the thicket, a much larger creature lets out a high-pitched vibration of mourning and hunger.

Variants

Mana-Gorged Swarm: Higher CR, deals additional force damage.
Shadow-Stitched Swarm: Found in the Shadowfell, causes necrotic damage instead of lightning.

Hooks

Plot hooks

The local druid grove has gone silent, and the path is now covered in shimmering, buzzing silk.
A merchant's caravan carrying mana crystals was swarmed; the crystals are gone, and the guards are stuck to the trees like living statues.
An eccentric wizard wants a jar of Silk-gnawers to study their magical conductivity.

How to use it

As a hazard in a larger forest chase scene.
As the 'doorbell' encounter before a giant spider boss fight.

Treasure

Silk-Gnawer Residue: Can be harvested (DC 15 Survival) to create 1d4 doses of Conductive Grease, which grants a weapon +1 lightning damage for 1 hour but imposes disadvantage on stealth.

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