Chaos Space Marine, Possessed (5e Creature)
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Large fiend (shapechanger), any evil alignment
Saving Throws Str +10, Con +10, Cha +8
Brute. A melee weapon deals one extra die of its damage when the chaos marine hits with it (included in the attack).
Devil’s Sight. Magical darkness doesn’t impede the chaos marine’s darkvision.
Magic Weapons. In its daemon form, the chaos marine’s natural weapons are magical.
Shapechanger. The chaos marine can use its action to polymorph into a daemon or back into its humanoid form. Its statistics are the same in each form. Any equipment it is wearing or carrying is transformed. It reverts to its true form if it dies.
Multiattack. In daemon form, the chaos marine makes three attacks: one with its bite and two with its claws. In humanoid form, it makes two chainsword attacks.
Bite (Daemon Form Only). Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 13 (3d4 + 6) piercing damage, and the target must succeed on a DC 16 Constitution saving throw or be poisoned for 1 hour.
Claw (Daemon Form Only). Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 19 (3d8 + 6) slashing damage.
Chainsword (Humanoid Form Only). Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 19 (3d8 + 6) slashing damage, or 22 (3d10 + 6) slashing damage if wielded in both hands.
Fire Breath (Daemon Form Only; Recharge 5-6). The chaos marine exhales magical fire in a 30-foot cone. All creatures within that area must make a DC 16 Dexterity saving throw, taking 33 (6d10) fire damage on a failed save, or half as much damage on a successful one.
Possessed marines are chaos space marines that have allowed fiends to inhabit their bodies. In return for eternal damnation, they gain increased resilience and the ability to turn into horrific, fire-spewing monsters.
Voluntary Possession. Chaos space marines will do almost anything to gain greater power and standing in the eyes of the Chaos Gods. Some are so brazen—or desperate—that they will allow daemons to be summoned into their bodies, binding the fiends to their very flesh and soul. This possession greatly enhances the chaos marine’s resilience and allows him to reshape his body into a nightmarish abomination with a thought.
Protean Horrors. No two possessed marines look alike in their daemonic forms. Some may sprout horns and scales all over their bodies. Some’s hands may morph into reptilian claws or crustacean pincers. Some grow additional eyes, or have no eyes at all (though this does not affect their senses in any way). Some may even sprout leathery wings from their backs, or have their arms turn into tentacles. Whatever twisted forms they take, possessed marines are a force to be reckoned with.
Power at a Price. Though the possession benefits the chaos marine greatly, it is not without its drawbacks. While the possessed marine inherits many of his fiendish tenant’s strengths, he also inherits its weaknesses, becoming susceptible to weapons and spells that never would have affected him when he was still “merely” a superhuman. Additionally, his fiendish passenger has a will of its own and may fight him for control over their shared body. Possessed marines with weak wills find their personas completely suppressed as the fiend takes full control of its fleshy vessel, while strong-willed ones can reach a sort of symbiosis with their daemonic passenger. Finally, the chaos marine's soul is damned for all eternity once he dies, doomed to be gnawed and devoured by the very daemon he hosted in life.
Variant: Flying Possessed
This chaos marine grows a pair of leathery wings when it transforms. It has a flying speed of 60 feet while in its daemon form, and gains the following trait.
Dive. If the chaos marine is flying and dives at least 30 feet straight toward a target and then hits it with a melee weapon attack, the attack deals an extra 9 (2d8) damage.
Variant: Grappler Possessed
One of the chaos marine’s arms morphs into a muscular tentacle when it transforms. It gains a tentacle attack in its daemon form and has the following traits. This does not affect the chaos marine’s challenge rating.
Multiattack. The chaos marine makes three attacks: one with its bite, one with its claw, and one with its tentacle.
Tentacle. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 19 (3d8 + 6) bludgeoning damage and the target is grappled (escape DC 18). Until the grapple ends, the target is restrained, the chaos marine can automatically hit the target with its tentacle, and the chaos marine can’t use its tentacle against another target.