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The Hollow Sentinel - AI-generated fantasy Monster

The Hollow Sentinel

General Valerius was the last shield of the Autumn Kingdom. When the kingdom fell to the Blight, his oath was so strong that the very thorns that slew him took root in his armor, using his memories to maintain a tireless, hateful vigil.

Monsters
Large construct · CR 13 · Unique

The Hollow Sentinel

A legendary elven general's plate armor possessed and reanimated by malevolent autumn briars.
AC19
HP195/195
CR13
Init
STR
DEX
CON
INT
WIS
CHA
ConditionsNone

Combat

AC 19 · HP 195 · CR 13

The Hollow Sentinel

Large construct (plant), lawful evil
Armor Class19 (Natural Armor)
Hit Points195 (17d10 + 102)
Speed
30 ft.
STR
DEX
CON
INT
WIS
CHA
Saving ThrowsStrengthConstitutionWisdom
SkillsAthleticsPerceptionIntimidation
Damage Resistances
Bludgeoning, Piercing, and Slashing from Nonmagical Attacks
Immunities
Poison,
Psychic,
Exhaustion,
Paralyzed,
Petrified,
Poisoned
Weaknesses
Fire
Senses
Blindsight 60 ft.,
Passive Perception 17
Languages
Common,
Elvish,
Sylvan
Challenge13
Proficiency Bonus+5
False Appearance. While the sentinel remains motionless, it is indistinguishable from a standard decorative suit of armor.
Thorny Carapace. A creature that hits the sentinel with a melee attack while within 5 feet of it takes 7 () piercing damage from the vines protruding through the armor.
Magic Resistance. The sentinel has advantage on saving throws against spells and other magical effects.

Actions

Multiattack. The sentinel makes three attacks with its Petrified Glaive.
Petrified Glaive. Melee Weapon Attack: to hit, reach 10 ft., one target. Hit: 16 () slashing damage plus 7 () poison damage.
Root Grasp (Recharge 5-6). The sentinel slams its glaive into the ground. Thorns erupt in a 20 foot radius centered on the sentinel. Each creature in that area must make a Strength saving throw. On a failure, a creature takes 21 () piercing damage and is Restrained. On a success, it takes half damage and isn't restrained. A restrained creature can use an action to make a Strength (Athletics) check to escape.

Reactions

Thorn Lash. When a creature moves out of the sentinel's reach, the sentinel can use its reaction to make a vine lash out. The target must succeed on a Dexterity saving throw or its speed is reduced to 0 until the start of its next turn.

Legendary Actions

Glaive Sweep. The sentinel makes one Petrified Glaive attack.
Creeping Vines. The sentinel moves up to its speed without provoking opportunity attacks.
Sapping Spores (Costs 2 Actions) (costs 2 actions). The vines release a cloud of amber dust. Each creature within 10 feet of the sentinel must succeed on a Constitution saving throw or be Blinded until the end of its next turn.
Role
Solo Dungeon Boss
Built for
Level 11 to 13

Gear

  • Glaive of the Fallen General (Magic Weapon, 5,000 gp)A glaive made of petrified Ironwood that deals bonus poison damage.
  • Ancient Elven Plate (Armor, 2,500 gp)Beautifully crafted brass plate armor with leaf motifs.

Feats

Sentinel
Polearm Master

Augmentations

Animated Vines: Provides reach and restraint capabilities.

Notes for the game master

The Sentinel is effectively a Construct/Plant hybrid.
Use Root Grasp early to split the party.
Fire damage suppresses Thorny Carapace for 1 turn.

Tactics

  1. Opening

    The Sentinel begins by using Root Grasp to lock down the front line and spellcasters alike.

  2. Mid-fight

    It uses Glaive Sweep to keep multiple targets at bay, prioritizing those who deal fire damage.

  3. End of the fight

    When below 50 HP, it uses Sapping Spores every round it can to ensure its escape or a final stand.

  4. Retreat

    It will never retreat, bound by its eternal oath. It fights until the armor is a heap of scrap and the vines are ash.

How it fights

Stay in the center of the room to maximize the reach of Root Grasp.
Use Legendary Actions to reposition constantly to avoid being flanked.
Target casters with the Petrified Glaive to break concentration on fire spells.

Who it attacks first

Fire-based Spellcasters
Mobile Rogues/Monks
Healers

Works well with

Shambling Mounds: Can hide in the room and be healed by lightning if the sentinel is modified.
Awakened Trees: To add more targets and control the battlefield.

How to beat it

Fireball or Burning Hands to disable the thorns.
Teleportation spells to escape Root Grasp.
Dispel Magic or Anti-Magic Field to weaken the animated armor (DM's discretion).

Ways to avoid a fight

Reciting the General's lost oath may cause the sentinel to pause for 1 round.
Offering a relic of the old king might allow the party to pass without a fight.

Ecology

A towering suit of ornate elven plate armor made of dull, verdigris-stained brass. Black, thorny vines snake through the joints and the open visor, pulsing with a faint, sickly amber light. It stands seven feet tall, holding a massive glaive carved from dark, petrified wood.

Behavior

It stands motionless until its sanctum is breached, then moves with a jerky, rhythmic clicking sound. It does not seek to kill immediately but to entangle and crush, speaking only in a voice that sounds like branches grinding against stone.

How it lives

Not a natural creature, but a symbiosis of a cursed plant spirit and elven metallurgy. It feeds on the decay of the kingdom it once protected.

Lair

The Autumnal Sepulcher, a chamber filled with knee-deep dead leaves, crumbling marble pillars, and thick carpets of grasping vines.

Habitat
Ruined Elven Throne Rooms, Ancient Forest Vaults, Desecrated Sylvan Shrines.

Signs that it is near

Patches of black, unnaturally sharp thorns on stone surfaces
The smell of dry rot and petrichor
Metal scrapings on the floor leading to a central dais

Tags

Guardian,
Possessed,
Blighted

Lore

General Valerius was the last shield of the Autumn Kingdom. When the kingdom fell to the Blight, his oath was so strong that the very thorns that slew him took root in his armor, using his memories to maintain a tireless, hateful vigil.

What drives it

To prevent anyone from reclaiming the crown or relics of the fallen Elven Dynasty.

After the fight

Upon defeat, the armor collapses into a pile of rust and the vines wither instantly into gray ash. A soft, relieved sigh echoes through the chamber as the General's spirit is finally freed.

Variants

Frozen Sentinel: Replace Fire weakness with Fire immunity and Cold weakness (Winter theme).
Blighted Sentinel: Poison damage is replaced with Necrotic damage.

Hooks

Plot hooks

The ghost of the General's daughter asks the party to put his restless spirit to peace.
The local forest is turning into a 'Thorn-Waste', and the source is the Sentinel's lair.

How to use it

Final boss of an Autumn-themed Elven dungeon.
The guardian of a seal that keeps a greater evil locked away.

Treasure

Glaive of the Fallen General (Rare)
3000 gold worth of ancient elven coins
A map to the Hidden Summer Court

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