Aegis Prime

Forged in Steel. Aegis Prime is tool of defense and gains a +2 to his AC when below half HP. 

Magic Resistance. Aegis Prime has advantage against spells and other magical effects 

Immovable Object. Aegis Prime is immune to being knocked prone, grappled and cannot be moved or shoved by nonmagical means. (flavor options for how Aegis 1 resists)
          1: Aegis Prime releases pressurized steam reserves to slick the surface of his body or  provide a burst of momentum to offset movement
          2: Aegis Primes's eyes and metal skin glow brighter and seem to reinforce itself against incoming attack

Divine Smite (at will/no cost). when you hit a creature with a melee weapon attack, you can expend one spell slot to deal radiant damage to the target, in addition to the weapon’s damage. The Extra damage is an additional 3d8 radiant damage.

Spellcasting.  Aegis Prime is a 10th level spell caster with Paladin spells 

1st level (4 slots): disguise self, searing smite

2nd level (4 slots): misty step, branding smite

3rd level (3 slots): blinding smite, spirit shroud

Multiattack. Aegis Primemakes two melee attacks.

Greatsword. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 7) slashing damage.

Mechanical Menace (Recharges after a Short or Long Rest). As an action, any creature that can see Aegis Prime's eyes within 60ft must make a DC 16 Wisdom saving throw or be frightened of Aegis for 1 minute. Any creature effected by this can repeat the save at the end of each of its turns. 

Parry. Aegis 1 adds 2 to its AC against one melee attack that would hit it. To do so, Aegis 1 must see the attacker and be wielding a melee weapon.