Ironwrought Enforcer
Traits
Immutable Form. Immune to any spell or effect that would alter its form.
Warrant of Arrest. The Ironwrought Enforcer marks a target as "to be arrested" (no Bonus Action required, declared at the start of combat). It attacks that target with Advantage, and the Grapple DC of Manacle Slam against it increases by +2.
Riot Line. Allies within 10 feet of the Ironwrought Enforcer gain Half Cover (+2 AC).
Actions
Multiattack. Makes three Manacle Slam attacks.
Manacle Slam. Melee Attack Roll: +12, reach 10 ft. Hit: 22 (3d10 + 7) Bludgeoning damage, and the target makes a DC 20 Strength save. Failure: The target has the Grappled condition (escape DC 20). The Ironwrought Enforcer can hold three creatures Grappled at once.
Subdue (Recharge 5–6). Every creature it holds Grappled makes a DC 20 Constitution save.
- Failure: 36 (8d8) Bludgeoning damage, and the target has the Restrained condition (escape DC 20) and its Speed becomes 0.
- Success: Half damage, and it is freed from being Grappled.
Reactions
Detain (3/Turn). When an enemy within 10 feet of the Ironwrought Enforcer moves away from it or attacks a target other than the Enforcer: the Enforcer makes one Manacle Slam attack.
How to Use
The city's force of order. But is it really "good"? A tyrant may be using it to arrest innocent people.
Detain (3/Turn) plus three Grapple slots means the party can't get past its line.
Key
Force damage (not on its Resistance list), teleportation, or not relying on control spells — Constructs are immune to most of them. Brute force is what's needed.