Magic Resistance- The acid mech has advantage on saving throws against spells or any other magical effects.

Magic Weapons- The acid mech's attack are magical. 

Immutable Form- The acid mech is immune to any spell or effect that would alter it's form. 

Acidic Blood- The body of an elemental fused with acid lives inside the mech. Anytime the mech takes damage, if the creature that dealt the damage in within 10 feet of the acid mech it takes 1d10 acid damage.

Multiattack- The Acid Mech makes two attack with his acid rifle.

Acid Splash- The acid mech opens up a compartment in his chest and sprays out a large amount of it's acidic blood in a 10 foot cone, any creature in the range of this attack must succeed a DC 15 Dexterity saving throw, taking 2d8+8 acid damage on a fail, or half as much on a success.

Acid Rifle Shot- Ranged Weapon Attack: +10 to hit, reach 60/120 ft., one target. On hit: 3d8+6 acid damage.

Acid Grenades (Recharge 5-6)-The acid mech throws a large grenade within 120 ft. of it, filled with his acidic blood, when it lands it explodes in a 15 foot radius of acid, anyone who starts their turn or enters the area for the first time must succeed on a DC 14 Dexterity saving throw, taking 6d8 acid damage on a fail, half as much on a success. 

Shove- If the acid mech moves at least 10 feet in a straight line towards a target, it can immediately use his bonus action to attempt to shove the target to the ground. The target must succeed on a DC 15 Strength saving throw or be knocked prone. The target takes 2d10 bludgeoning damage as the acid mech rolls over them.