Clockwork Centurion

Variable Anatomy. The clockwork centurion is immune to critical hits.

Multiattack. The clockwork warrior makes two attacks with its fists, two attacks with its blade, or two needler attacks. It may also make one attack with its needler and one melee attack at disadvantage. 

Fist. Melee Weapon Attack: +6 to hit, reach 15 ft., one target. Hit: 25 (3d12 + 5) bludgeoning damage. 

Blade. Melee Weapon Attack: +6 to hit, reach 20 ft., one target. Hit: 22 (3d10 + 5) slashing damage. 

Needler. Ranged Weapon Attack: +3 to hit, range 50/200 ft., one target. Hit: 10 (2d8 + 1) piercing damage.

Flamer. The clockwork warrior uncovers a flame projector and spews forth a gout of flame in a 15 foot cone. Each creature in the target area must make a DC 16 Dexterity saving throw, taking 18 (4d8) fire damage on a failed save or half as much on a successful one. Flammable objects in the target area are ignited.

Steam Breath (Recharge 5-6). The clockwork unleashes a torrent of steam from the top of its form in a 30 foot cone. Each creature in the target area must make a DC 16 Constitution saving throw, taking 8d8 (36) fire damage on, and being poisoned until the end of the centurion's next turn, or half as much on a successful one. Creatures that failed the save take an additional 18 (4d8) fire damage at the start of each of the next three of their turns unless they make a DC 16 Constitution save.

Sonic Pulse (Recharge 6). A sonic pulse erupts from the clockwork centurion. Creatures with 15 feet of it must make a DC 15 Constitution saving throw taking 12 (4d6) thunder damage and being stunned, and deafened for one minute. Stunned creatures may make a DC 13 Constitution at the start of each of their turns to remove the stunned condition. 

Recombination (Recharge 5-6). The clockwork warrior makes changes to its overall form to make different functions. It can choose between one of the three modes below:
Flight Mode: The clockwork warrior gains a flying speed of 40 ft.
Juggernaut Mode: The clockwork warrior increases its armor class by 2, and deals an extra 5 damage with its weapon attacks of a type that the weapon would deal. Its speed decreases to 20 ft.
Sentry Mode: The clockwork warrior gains a +5 bonus to its Wisdom (Perception) checks, gains a 120 ft. Blindsense and its first opportunity attack per turn does not count as a reaction.