Iron Golem

Whenever the golem is subjected to Fire damage, it regains a number of Hit Points equal to the Fire damage dealt.

The golem can't shape-shift.

The golem has Advantage on saving throws against spells and other magical effects.

The golem makes two attacks, using Bladed Arm or Fiery Bolt in any combination.

Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 27 (3d8 + 7) slashing damage plus 7 (2d6) fire damage.

Ranged Weapon Attack: +12 to hit, range 120 ft., one target. Hit: 36 (8d8) fire damage.

The golem exhales poisonous gas in a 60-foot cone. Each creature in that area must make a DC 18 Constitution saving throw, taking 55 (10d10) poison damage on a failed save, or half as much damage on a successful one.