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Mycelial Sentinel - AI-generated fantasy Monster

Mycelial Sentinel

Legend speaks of the Verdant Guard, an elite elven unit that stayed behind to hold the line against a creeping rot. They succeeded in stopping the rot's spread, but at the cost of their autonomy. Now, they are the very thing they fought, turned into mindless puppets by the fungal spores they inhaled during their final stand.

Monsters
Medium plant · Moderate · Rare

Mycelial Sentinel

Parasitized elven guardians
AC17
HP85/85
CRModerate
Init
STR
DEX
CON
INT
WIS
CHA
ConditionsNone

Combat

AC 17 · HP 85 · Moderate

Mycelial Sentinel

Medium plant (elf), lawful neutral
Armor Class17 (Natural Armor and Elven Plate Fragments)
Hit Points85 (10d8 + 40)
Speed
30 ft. walk
STR
DEX
CON
INT
WIS
CHA
Saving ThrowsDexterityConstitution
SkillsStealthPerceptionAthletics
Damage Resistances
Bludgeoning,
Piercing
Immunities
Poison,
Charmed,
Exhaustion,
Frightened
Weaknesses
Fire,
Radiant
Senses
Blindsight 60 ft. (Blind beyond this radius),
Passive Perception 14
Languages
Understands Elvish but cannot speak
ChallengeModerate
Proficiency Bonus+3
Fungal Regrowth. The sentinel regains 10 hit points at the start of its turn if it is in dim light or darkness. If the sentinel takes fire or radiant damage, this trait does not function at the start of its next turn. The sentinel dies only if it starts its turn with 0 hit points and does not regenerate.
Jerky Coordination. The sentinel's movements are unpredictable. It has advantage on Dexterity saving throws and creatures have disadvantage on opportunity attacks against it.
False Appearance. While the sentinel remains motionless, it is indistinguishable from a fungus-covered statue or a pile of armor.

Actions

Multiattack. The sentinel makes two Rotting Glaive attacks.
Rotting Glaive. Melee Weapon Attack: to hit, reach 10 ft., one target. Hit: 8 () slashing damage plus 7 () necrotic damage. If the target is a creature, it must succeed on a Constitution saving throw or its maximum hit points are reduced by an amount equal to the necrotic damage taken.
Spore Cloud (Recharge 5-6). The sentinel releases a burst of yellow spores. Each non-plant creature within 10 feet of the sentinel must make a Constitution saving throw. On a failure, a creature takes 18 () poison damage and is blinded until the end of its next turn. On a success, it takes half as much damage and isn't blinded.

Reactions

Fungal Reprisal. When a creature within 5 feet hits the sentinel with a melee attack, the sentinel can release a puff of caustic gas. The attacker takes 5 () acid damage.
Role
Area Denial Tank
Built for
5

Gear

  • Sunder-Steel Glaive (Weapon, 25 gp (Salvage value))An ancient elven polearm pitted with rust and dripping with black ichor.
  • Fused Plate (Armor, Non-removable)Fine elven plate armor rendered unusable by root-like fungal growths.

Feats

Sentinel
Polearm Master

Augmentations

Mycelial Nervous System (provides Blindsight and immunity to mind-affecting effects)

Notes for the game master

Remember that the 10 ft. reach is its primary advantage.
The healing only stops if fire or radiant is used.
Blindsight allows it to fight effectively in its own Spore Cloud.

Tactics

  1. Opening

    The Sentinels wait for the party to enter a narrow corridor before detonating their Spore Clouds to blind the front line.

  2. Mid-fight

    They use their 10 foot reach to attack over each other's shoulders, staying in the dim light of the corridor to trigger Fungal Regrowth.

  3. End of the fight

    If reduced to low health, they clump together, using their reactions to punish any melee attackers while their allies cycle to the front.

  4. Retreat

    The sentinels never retreat. They fight until their bodies are completely incinerated or reduced to mulch.

How it fights

Always stay in dim light or darkness to maximize healing.
Focus attacks on the same target to maximize the HP reduction from the Rotting Glaive.
Use opportunity attacks from the Sentinel feat to stop PCs from moving past them.

Who it attacks first

Characters dealing fire or radiant damage to stop the healing.
Light-bearing characters (cleric/paladin) to extinguish sources of bright light.
Weak-looking casters who might have low Constitution saves.

Works well with

Pairs well with Gas Spores or Violet Fungi for a total fungal theme.
Shambling Mounds can absorb the lightning or move with them to provide cover.
A Spore Druid NPC can command them and provide magical darkness.

How to beat it

Daylight or Continual Flame spells create bright light that negates Fungal Regrowth.
Fireball or Burning Hands to deal area fire damage.
Forcing the sentinels into direct sunlight or out of the Root-Hall corridors.

Ways to avoid a fight

An Elf character might recognize the armor and perform an ancient elven burial chant, which could temporarily pacify the sentinels for 1 minute.
Creatures covered in the scent of the Maw's queen fungus are ignored by the sentinels.

Ecology

A tall, slender figure clad in tarnished elven plate. Thick, shelf-like fungi erupt from the seams of the armor, effectively welding the metal to the gray, shriveled skin beneath. Pale mycelial threads wrap around its limbs like biological wire. Where eyes once were, bioluminescent mold glows with a dim, sickly green light. It moves with a staccato, twitching motion, as if its muscles are being pulled by external strings.

Behavior

The sentinels stand perfectly still until their corridor is breached. They do not speak, producing only the sound of rubbing dry wood or wet soil. They operate with a collective intelligence, shifting and flanking in total silence. They prioritize blocking exits and maintaining positions in the shadows of the Root-Hall.

How it lives

A symbiotic nightmare. When an elven defender dies in the Maw of Moss, a specific strain of parasitic cordyceps colonizes the nervous system and the metal of the armor. The fungus feeds on the lingering magical resonance in the elf's bones, keeping the corpse animated as a permanent security system for the fungal colony.

Lair

Transition corridors between the Root-Hall and the Maw of Moss. These hallways are choked with spore-laden mist and carpeted in thick, damp moss.

Habitat
Deep forests, fungal caverns, and overgrown elven ruins.

Signs that it is near

Patches of glowing green mold in the shape of bootprints
A faint, rhythmic clicking sound echoing off corridor walls
Dried elven blood mixed with white fungal filaments
Discarded elven arrows overgrown with puffballs

Tags

Fungal,
Blighted,
Undead-Adjacent,
Guardian

Lore

Legend speaks of the Verdant Guard, an elite elven unit that stayed behind to hold the line against a creeping rot. They succeeded in stopping the rot's spread, but at the cost of their autonomy. Now, they are the very thing they fought, turned into mindless puppets by the fungal spores they inhaled during their final stand.

What drives it

To prevent non-fungal life from entering the Maw of Moss and to provide fresh organic matter for the fungal hivemind.

After the fight

Once defeated, the sentinel's body collapses into a pile of harmless, quickly decaying compost. The elven spirit is finally at rest, but the spores lingering in the air may require the party to burn their clothes to prevent further infection.

“They succeeded in stopping the rot's spread, but at the cost of their autonomy.”
From its lore

Variants

Mycelial Archer: Swaps the Glaive for a Longbow that fires toxin-tipped arrows.
Spore-Lord: A CR 8 version with the ability to cast 'Cloudkill' once per day.

Hooks

Plot hooks

The party is hired to recover a family heirloom from the corpse of an elven knight last seen entering the Root-Hall.
The local druid circle reports that the sentinel population is expanding out of the corridors and into the main forest.
A strange fungal infection in the nearby village matches the spores found on a salvaged elven glaive.

How to use it

Guardians of a transition zone between two major forest dungeons.
Ambush predators in a heavily obscured fungal forest.
The tragic remnants of a hero's lost expedition.

Treasure

1d4 Violet Fungus Spores (can be used as poison)
Ancient Elven Signet Ring (worth 50 gp)
Pouch of phosphorescent moss (can be used as a temporary torch)

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