Gearkeeper Construct
Large Construct, UnalignedHabitat Dungeon, Underdark
Resembling a rolling ball of shield-like plates, a gearkeeper construct can rapidly travel through corridors to seek intruders. Upon discovering an unrecognized creature, the shields expand to reveal gaps where numerous metallic legs emerge for precision movement. Bladed appendages whir around the construct, threatening any unlucky delvers who wander too close, while heavy spears of steel can be fired from within the construct's core, impaling unwanted guests. If overwhelmed, the construct can discharge a spray of heated, jagged metal fragments to subdue groups of intruders.
Reverse engineering from the recovered shells and scraps of excavated gearkeeper constructs, a number of modern tinkerers have developed updated variations of these sentinels. Such designs are only recently seeing use in select prisons, or by wealthy collectors seeking to keep their collections safe.
Constructed Nature. A gearkeeper construct doesn't require air, food, drink, or sleep.
AC 18 (natural armor)
HP 161 (17d10 + 68)
Speed 60 ft.
STR
20 (+5)
Save +5
DEX
16 (+3)
Save +3
CON
18 (+4)
Save +4
INT
3 (-4)
Save -4
WIS
11 (+0)
Save +0
CHA
1 (-5)
Save -5
Resistances Bludgeoning, Piercing, and Slashing from nonmagical attacks
Immunities Fire, Poison, Psychic
Condition Immunities Charmed, Exhaustion, Frightened, Paralyzed, Petrified, Poisoned
Senses Blindsight 120 ft., Passive Perception 10
Languages Understands the languages of its creator but can't speak
CR 10
Traits
Immutable Form. The gearkeeper is immune to any spell or effect that would alter its form.
Rapid Shifting. Opportunity attacks made against the gearkeeper have Disadvantage.
Whirling Blades. Any creature that starts its turn within 5 feet of the gearkeeper takes 4 (1d8) Slashing damage.
Actions
Multiattack. The gearkeeper makes two Arm Blade attacks, or one Arm Blade attack and one Spear Launcher attack.
Arm Blade. Melee Attack Roll: +9, reach 5 ft. Hit: 18 (3d8 + 5) Slashing damage.
Spear Launcher. Ranged Attack Roll: +9, range 90 ft. Hit: 12 (2d6 + 5) Piercing damage, and the target has the Prone condition.
Shrapnel Blast (Recharge 6+). The gearkeeper jettisons a spray of jagged metal in a 30-foot Cone. Each creature in the area must make a DC 15 Dexterity Saving Throw, taking 21 (6d6) Piercing damage on a failed save, or half as much damage on a successful one.