Ancient Sentinel
Legend speaks of ancient constructs built to hold back a terribly calamaity of untold horrors from beyond. Posted as eternal guards over ancient lost portals, these construct sentinels were thought to be immune to whispers of madness that seeped through... a theory that has proved tragically misguided. Now twisted by the forces beyond, the sentinels have warped into eldritch engines of destruction, completely mad and not truly aware of their own actions.
Awakening from ancient forgotten sites, often long lost vaults and shrines, these can appear without warning and wreck terrible destruction in a maddened rampage.
These sentinels are massive creatures from an ancient era, towering 30 feet tall, easily crushing anything built to a human scale with ease.
Tactics
Deployment
The Ancient Sentinel is intended primarily a solo encounter, and particularly excels as an event. A rampaging gigantic mechanical elephant is most dramatic when it has plenty of buildings (and maybe some villagers) to trample (and for the players to save). It is a siege monster that excels at engaging many targets. It can even enter a campaign a little earlier then its CR might suggest as a set piece encounter where the PCs are rallying a defense against it.
If you do need some more chaos, you can have the Ancient Sentinel be the harbriger to a wave of psionic monsters that broken through in its wake. It's immunity psychic damage makes it largely immune to many of their effects, making it a devastating pairing.
Simple Script
Here's a simple script the you can follow to get an effective use from the Ancient Sentinel.
- The sentinel should always move when possible, ideally trampling any smaller creatures in its path and smashing buildings of possible. Move for maximum destruction unless it has a specific objective.
- Move towards something that can be smashed.
- During the advance, unleash a Bladed Trunk attack at something into or out of its path. It can use bladed trunk.
- Move through a target using Trampling Advance.
- If it knocks a target prone or is is moving through its last target, use stomp.
- Lastly, it should lash out with its tentacles against any target that is attacking it, either grabbing or flinging things at the attacks.
- If a target is bothering it with ranged attacks, it can fling creatures or objects it is grappling at it.
Considerations
While the sentinel lacks ranged abilities, it can use fling as a ranged offensive tool quite effectively if needed simply by picking up objects and flinging them. While its movement speed is not particularly high, its Unstoppable Advance and Trample legendary action mean its effective movement can be quite substantial.
The sentinel may not care about the party at all. If they are insufficiently powerful to stop it, it may simply rampage through a city before wandering off to rampage elsewhere. Only if players prove a danger to it will it focus on them.
While a very challenging monster, the dynamic nature of the fight will come from what the sentinel is destroying.
Ancient Sentinel
Gargantuan construct, chaotic evil
- Armor Class 18 (natural armor)
- Hit Points 297 (17d20 + 119) [Max: 459]
- Speed 40 ft.
STR DEX CON INT WIS CHA 26 (+8) 6 (-2) 24 (+7) 7 (-2) 16 (+3) 13 (+1)
- Saving Throws Strength +14, Con +11, Wis +7, Cha +5
- Skills Athletics +12, Perception +7
- Damage Resistances bludgeoning, piercing, and slashing from nonmagical attacks that aren't adamantine
- Damage Immunities poison, psychic
- Condition Immunities charmed, exhaustion, frightened, paralyzed, prone, petrified, poisoned
- Senses blindsight 60 ft., darkvision 120 ft., passive Perception 17
- Languages understands deep speech, but can't speak.
- Challenge 19 (20,000 XP) Proficiency Bonus +6
Magic Resistance. The sentinel has advantage on saving throws against spells and other magical effects.
Immutable Form. The sentinel is immune to any spell or effect that would alter its form.
Legendary Resistance (3/Day). If sentinel fails a saving throw, it can choose to succeed instead.
Siege Monster. The sentinel deals double damage to objects and structures.
Scale Immunity. The sentinel resistance to the damage of any spell that does not target and area of effect, and suffers no other conditions or effects from them.
Trampling Advance. Any Large or smaller creature in a space the sentinel passes through must make a DC 16 Dexterity saving throw or take 13 (2d12) bludgeoning damage and be knocked prone.
Unstoppable Advance. The sentinel's advance cannot be stopped. If the sentinel's speed would be reduced to zero, it is reduced to half its movement speed instead. Any obstacle or building that would stop its advance takes 39 (6d12) bludgeoning damage. The sentinel treats magical barriers that would stop its movement as difficult terrain.
Whispering Madness. The sentinel is steeped in eldritch madness. If a creature starts its turn while within 5 ft of the sentinel or while grappled by it, it must pass a DC 16 Wisdom saving throw, or take 3d6 psychic damage and roll a d4, suffering an additional condition until the start of their next turn.
d4 Condition 1-2 Frightened 3 Blinded 4 Paralyzed
Bloodied
If the sentinel is bloodied (reduced to less than half of its maximum hit points), it unleashes a psionic blast immediately (no action required), violently discharging the eldritch corruption within it. All creatures within 60 feet of it must make a DC 16 Intelligence saving throw. On failure, they take 6d6 psychic damage and become stunned until the end of their next turn. On success, they take half as much damage and are not stunned. The range of Whispering Madness then increases to 60 feet until the sentinel dies or recovers hit points above half its maximum.
Actions
Multiattack. The sentinel will makes a bladed trunk attack, a stomp attack, and two tentacle attacks. It can replace each tentacle attack with one use of Fling. It can move between of these attacks.
Stomp. Melee Weapon Attack: +14, reach 5ft., one target. Hit 27 (3d12 + 8)
Tentacle. Melee Weapon Attack: +14 to hit, reach 20 ft., one target. Hit: 18 (3d6 + 8) bludgeoning damage, and the target is grappled (escape DC 16). Until this grapple ends, the target is restrained. The sentinel has four tentacles, each of which can grapple one target.
Fling. One Large or smaller object held or creature grappled by the sentinel is thrown up to 60 feet in a direction of the sentinel's choice and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 16 Dexterity saving throw or take the same damage and be knocked prone.
Bladed Trunk. Melee Weapon Attack: +14, reach 5ft., one target. Hit 27 (3d12 + 8). On hit, the target must make a DC 16 Strength saving throw, or be knocked 10 feet in a direction of the sentinel's choice.
Legendary Actions
The sentinel can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The sentinel regains spent legendary actions at the start of its turn.
Unstoppable Trample. The sentinel moves up to half of its movements speed. This movement does not provoke attacks of opportunity.
Tentacle Attack or Fling. The sentinel makes one tentacle attack or uses its Fling.