Clockwork Soldier

Immutable Form. The Clockwork Soldier is immune to any spell or effect that would alter its form. 

Enduring Craftsmanship. The Clockwork Soldier has four sword-mounted arms. Whenever it takes 40 or more damage in a single turn, one of its limbs is destroyed. Roll a d6, on a 1-5, an arm is destroyed, on a 6, its head is destroyed. If its head is destroyed or it is unable to see, it will use sound to locate targets within 30 feet, it will attack any creature that it can sense while in this state. If all arms are destroyed, the Clockwork dies.

Hydraulic Joints. The Clockwork Soldier has advantage on Strength (Athletics) checks and its falling damage is halved. It also automatically fails Dexterity (Stealth) checks that rely on moving silently.

Overheat. Every 3 turns the Clockwork Soldier takes, or every time it suffers Fire or Lightning damage, it must make a DC 14 Constitution saving throw or overheat and be incapacitated until the end of its next turn as it cools down. While cooling down it immediately uses Repair if it is available and after cooling down it is immune to this effect until the end of its next turn.

Multiattack. The Clockwork Soldier makes as many Sword-Mounted Arm attacks as it has arms.

Sword-Mounted Arm. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit 11 (1d10 + 6) Slashing damage. 

Kick. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit 9 (1d6 + 6) Bludgeoning damage. The target must succeed on a DC 15 Strength saving throw or be pushed back 10 feet or knocked prone (Clockwork Soldier's choice).

Electrical Discharge. Ranged Weapon Attack: +2 to hit, range 30/90 ft., 1 target. Hit: 6 (1d8 + 2) Lightning damage. The target must succeed on a DC 10 Constitution saving throw or be stunned until the beginning of the Clockwork Soldier's next turn.

Repair (3/Day). The mechanisms inside of the Clockwork Soldier repair themselves, restoring 17 (3d8 + 4) hit points to itself.

Ancient Music (Recharge 5-6). The Clockwork Soldier's internal mechanisms emit a deafening composition of musical notes that suppresses magical effects. Every creature within 15 feet of the Clockwork Soldier must make a DC 12 Constitution saving throw or be Stunned until the beginning of the Clockwork Soldier's next turn. For the next 12 seconds (or two rounds) or until its concentration breaks (as if concentrating on a spell), all magic that comes within 20 feet of the Clockwork Soldier is immediately disrupted, as if affected by the antimagic field spell.