Clockwork Wall

Immutable Form. The clockwork soldier is immune to any spell or effect that would alter its form.
Magic Resistance. The clockwork soldier has advantage on saving throws against spells and other magical effects.
Magic Weapons. The clockwork soldier's weapon attacks are magical.
Death Burst. When the clockwork soldier dies, it explodes. Each creature within 5 feet of it must make a DC 13 Dexterity saving throw, taking 7 (2d6) fire damage on a failed save, or half as much damage on a successful one.

Adaptable defenses. Whenever the Clockwork Wall is successfully hit by an attack, its AC increases by 1 until the start of its next turn(to a maximum of 22) and it gains 3 (1d4+1) temporary hit points.

Programmed Maneuver. The Clockwork Wall is programmed with the following combat feature.

Reckless attack programming.  

The Clockwork Wall makes an attempt to draw aggression from its allies by making a more accurate, but reckless strike. When the Clockwork Wall makes the first attack on its turn, it can decide to attack recklessly. Doing so gives it advantage on melee weapon attack rolls using Strength during this turn, but attack rolls against the Clockwork Wall have advantage until its next turn.

Multiattack. The Clockwork Wall makes two shortsword attacks.

Shortsword. Melee weapon attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6+3)