IT'S ALIVE, kinda. Whenever Adam the Necrobarian is subjected to lightning or necrotic damage, it takes no damage and instead regains a number of hit points equal to the lightning or necrotic damage dealt.

Perfectly Constructed. Adam the Necrobarian is immune to any spell or effect that would alter its form.

Undead Resilience. Adam the Necrobarian has advantage on saving throws against spells and other magical effects.

Magical Creation. Adam the Necrobarian's attacks are magical. Adam's attacks count as lightning and necrotic damage for resistances, immunities, and vulnerabilities.

Multiattack. The Adam the Necrobarian makes one ranged attack and two melee attacks.

Ichorous Organ. Ranged Weapon Attack: +13 to hit, range 60 ft./120ft, reach 30ft. Sphere. Hit: 32 (6d8 + 8) necrotic damage.

Crushing Fists. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 23 (3d10 + 7) bludgeoning damage.

Voltaic Discharge (Recharge 4-6). Adam the Necrobarian surges  with intense channeled lightning. Each creature in that area must make a DC 20 Dexterity saving throw, taking 42 (14d6) lighting damage on a failed save, or half as much damage on a successful one.

As a bonus action Adam the Necrobarian may Rage, giving itself advantage on all attacks and resistance against bludgeoning, piercing, and slashing magic damage attacks. 

 Adam the Necrobarian may make a leap towards the last creature to hit him with a ranged attack.

Unliving Conduit Whenever Adam the Necrobarian is hit with a Melee Weapon Attack with a metal weapon or Unarmed Weapon Attack, attacking creature takes  4 (4d4) lighting damage.