Sources
CR
Type
Size
Alignment
Movement

Clockwork Oaken Bolter

Medium Construct, Unaligned

Armor Class 16 (natural armor)
Hit Points 117 (18d8 + 36)
Speed 30 ft.
STR
12
+1
DEX
18
+4
CON
15
+2
INT
3
-4
WIS
10
+0
CHA
1
-5
Damage Immunities poison
Condition Immunities Charmed, Exhaustion, Frightened, Paralyzed, Petrified, Poisoned
Senses darkvision 60 ft., passive Perception 10
Languages understands one language of its creator but can't speak
Challenge 5 (1,800 XP)

Traits

Magic Resistance. The clockwork has advantage on saving throws against spells and other magical effects.

Unusual Nature. The clockwork doesn't require air, food, drink, or sleep.

Actions

Multiattack. The clockwork makes two Lancing Bolt attacks or one Lancing Bolt attack and one Harpoon attack.

Lancing Bolt. Melee or Ranged Weapon Attack: +7 to hit, reach 5 ft. or range 100/400 ft., one target. Hit:15 (2d10 + 4) piercing damage.

Harpoon. Ranged Weapon Attack: +7 to hit, range 50/200 ft., one target. Hit:9 (1d10 + 4) piercing damage, and the target is grappled (escape DC 12). While grappled in this way, a creature's speed isn't reduced, but it can move only in directions that bring it closer to the clockwork. A creature takes 5 (1d10) slashing damage if it escapes from the grapple or if it tries and fails. The clockwork can grapple only one creature at a time with its harpoon.

Explosive Bolt (Recharge 5–6). The clockwork launches an explosive charge at a point within 120 feet. Each creature in a 20-foot-radius sphere centered on that point must make a DC 15 Dexterity saving throw, taking 17 (5d6) fire damage on a failed save, or half as much damage on a successful one.

Bonus Actions

Reel In. The clockwork pulls the creature grappled by its Harpoon up to 20 feet closer.

Lore

Gnomes' tinkering with magic and mechanical devices has produced many failed Constructs but also has resulted in genuine advances, such as clockworks. The methods used to craft clockworks have been shared between gnome communities over many generations.