Caelatores

Upholder of the Law. The Caelatores cannot willing break any laws of the area in which it is in. This means that it prefers to immobilize enemies. 

Mechanical Construct. The Caelatores takes the shape of a tall knight in grey armour. Although it is not imminently obvious, the Caelatores is a mechanical construct and does not need to eat or sleep. It will pursue its target relentlessly unless it acquires another target that has committed a more serious crime. It requires repair once a year and if it is destroyed. If damaged in combat, it will cast Mending on itself.

Spellcasting. The Caelatores is imbued with a magical energy source and is a 3-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 13, +5 to hit with spell attacks). The Caelatores has following Wizard spells prepared:
Cantrips (at will): Light, Shocking Grasp, Mending

1st level (4 slots): Shield, Detect Magic, Sleep

2nd level (2 slots): Hold Person, Detect Thoughts

Multiattack. The Caelatores makes 2 attacks with its Longsword.

Stun Staff. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 10 (2d6 + 3) bludgeoning and 4 (1d6) lightning damage. If a creature is holding or wearing metal, it must make a DC 13 CON save when hit. On a failed save, the creature must drop any metal items they are holding and are stunned until the start of their next turn if they are wearing metal armour.

Longsword. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 9 (1d10 + 3) slashing damage.

Heavy Crossbow. RangedWeapon Attack: +4 to hit, range 100/400 ft., 1 target. Hit: 7 (1d10 + 1) piercing damage.

Call for Backup. As an action, the Caelatores can emit a high pitched whistle that will alert any other Caelatores within 200ft that it requires help.

Parry: The Caelatores adds 2 to its AC against one melee attack that would hit it. To do so, the Caelatores must see the attacker and be wielding a melee weapon.