Clockwork Enforcer

Immutable Form: The Enforcer is immune to any spells or effects that would alter it's form.

Sturdy Build: The Clockwork Enforcer has advantage on saving throws that cause it to be knocked prone or be pushed back.

Legendary Resistance (1/day). If the enforcer fails a saving throw, it can choose to succeed instead. 

Multiattack. The Enforcer makes three attacks, two with it's Steam Glaive and one with it's Steam Cannon.

Steam Glaive. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) slashing damage. 

Steam Cannon. Ranged Weapon Attack: +8 to hit, range 120/480 ft., one target. Hit: 22 (4d10) force damage. Target must make a DC 16 Strength saving throw or be pushed back 10 ft. and be knocked prone.

Steam Blast (Recharge 5-6). The enforcer releases a concentrated blast of steam in a 30-ft. cone. Each creature in that area must make a DC 16 Dexterity saving throw, taking 28 (8d6) fire damage on a failed safe, or half as much on a successful one.  

Steam Shield. When the Enforcer is hit by a ranged attack, it can use it's reaction to unleash a burst of steam, imposing disadvantage against the attack.