Battle Mech

Pilot controlled. The Mech itself is not a being. there for it takes on the Wisdom, Intelligence, and charisma of the pilot. if the Mech is destroyed the pilot will still be alive at 1 hp. if the pilot gets out of the Mech the pilot will return to its max hit points or the current hit points of the Mech, whichever is lower  

Immutable Form. The Mech is immune to any spell or effect that would alter its form.

Magic Resistance. The Mech has advantage on saving throws against spells and other magical effects.

Magic Weapons. The Mech's weapon attacks are magical.

Magic Shielding. The Mech has a magical shield that dampens the damage it takes. The Mech is resistant to all melee or ranged attacks unless it beats the Mechs AC by 5 

Multiattack. The Mech makes two melee attacks. One sword attack and one slam attack

Slam. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 20 (3d8 + 7) bludgeoning damage.

Sword. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 23 (3d10 + 7) slashing damage.

Flamethrower (Recharge 5–6). The Mech sprays fire in a 30-foot cone. Each creature in that area must make a DC 17 Dexterity saving throw, taking 56 (16d6) fire damage on a failed save, or half as much damage on a successful one.

The Battle Mech can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Mech regains spent legendary actions at the start of its turn.

Detect. The Mech makes a Wisdom (Perception) check.

Poison Canisters (3 per day). The Mech exhales poisonous gas in a 15-foot radius. Each player must make a DC 17 Constitution save or lose their actions coughing and take 2d6 poison damage

Harpoon and reel. Ranged Weapon Attack +5 to hit, range 60/80, one target. Hit 10(1d10+4) piercing damage. the target will also have to make a DC 18 strength or be pulled to the Mech