Cannith Mechanical Guardian

Nightvision sensors. The Mechanical Guardian has darkvision in a range of 120 ft. 

Lacking consciousness. The Mechanical Guardian is immune to psychic damage, and to the charmed and frightened conditions. Moreover, it is immune to the effects of spells such as Detect Thoughts.

Stun Baton. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 1d4 + 2 bludgeonning damage and 1d6 lightning damage. The target must roll a DC 15 Constitution saving throw. On a failure, the target is stunned for its next turn, and it gains advantage on its next saving throw againt being stunned. 

Repair (3/Day). The magical mechanisms inside the Mechanical Warrior restore 2d8 + 2 hit points to itself or to one construct or object within 5 feet of it.

Magic Shield (2/Day). The Mechanical Guardian summons a magic force-field, cancelling the effect of all spells targeting it (this includes area-of-effect spells). The force-field remains until the Mechanical Guardian's next turn.