Radiant Golem

Name: Radiant Golem
Huge Construct, True Neutral w/ Neutral Good tendencies 

Attributes 
Str: 25 / +7
Dex: 9 / +1
Con: 24 / +7
Int: 8 / -1
Wis: 14 / +2
Cha: 10 / +0

Info 
AC: 20 (Natural Armor)
HP: 315 (18d12 + 198)
Speed: 30 ft.

Saving Throws: Con +14, Wis +9, Cha +7

Damage Resistance: Bludgeoning, Piercing, and Slashing from non-magical weapons

Damage Immunities: Lightning, Poison, Psychic

Condition Immunities: Charmed, Exhaustion, Frightened, Paralyzed, Petrified, Poisoned

Senses: Darkvision 120 ft. / Perception: +2 / 12

Languages: Understands all languages; telepathy 120 ft.

CR: 18 / PB: +6

Traits 

Construct Nature - The Radiant Golem does not require air, food, drink, or sleep

Radiant Regeneration - At the end of each of its turn, the radiant golem regains 10 (3d6) hit points if it at least has 1 hit point remaining. This regeneration is suppressed until the end of its next turn if it takes cold damage.

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

Magic Resilience - The radiant golem has advantage on Saving Throws against spells and other magical effects.

If the radiant golem succeeds on a Saving Throw against a spell, it takes no damage instead of half damage.

Fire Absorption - Whenever the radiant golem would take fire damage, it instead regains hit points equal to half the fire damage dealt.

Lightning Inertia - When the radiant golem takes damage, it takes no damage and becomes Slowed until the end of its next turn.

Death Aura (Mythic Hazard) - The radiant golem constantly emits a lethal magical aura.

• A creature that spends 1 continuous hour within 30 feet of the golem must succeed on a DC 18 Constitution Saving Throw at the end of that hour.
• On a failure, the creature's hit point maximum is reduced by 2d6.
• This reduction cannot be restored by anything short of a wish.
• If a creature's hit point maximum is reduced to 0, it dies with no death save.
• A creature that succeeds on the save is immune to this aura for 24 hours.

The radiant golem is completely unaware that this aura exists and cannot suppress it.

Actions 

Slam - Attk: +13 / D: 6d10+7 / R: Melee / Special: Reach

Specialized Traits 

Gentle Colossus - The radiant golem will never initiate combat unless escape is impossible. When attacked, it attempts to withdraw, telepathically pleading for peace.

Reluctant Defender - If reduced below half its hit points and unable to flee, the radiant golem fights defensively, focusing only on those actively attacking it.

Immortal Perspective - The golem does not understand mortality. It assumes all living beings are simply short-lived and view death as an unfortunate but natural occurrence.

Notes 

• The Radiant Golem is a one of kind construct found in Wild Space on the decaying world of Svalinn. The swathe of destruction to plant and animal life is caused by the unintended actions of the Radiant Golem, who was an iron golem forged from an iron ore mined out of the ore found in the center of a meteor. The metal skin of the radiant golem combined with the spark of life that gives it sentience has created a 'Death Aura' that will kill plant and animal life after a period of exposure.
• The Radiant Golem wanders the region, attempting to find friends among the mortals. While some adventuring groups have tried to adopt the golem, those that have remained long term companionship eventually succumb to the aura. The golem does not understand what is radiating from its body is what is killing its friends, leaving the radiant golem to bemoan that it has yet to maintain a friend that it is desperately searching for.
• The radiant golem has become a project for the Tabor-Armatrak Gnome clan who are using Svalinn for a mining colony. The gnomes have so far been able to develop a series of encased suits that allow them to deal with the radiant golem's gentle nature combined with its unintended death aura. The suits either lessen or block the aura at the cost of being cumbersome and requiring air tanks. The clan continues to test and try to find a method of solving the issue as they recognize the friendly golem could be an asset to the clan.