I thought I’d do something a little different for the season. There are a lot of themes that might scare your players, but few are so thorough as simulated body horror.
The Formless Horror is a creature from the nightmare of the imagination. It takes any shape, but it is not entirely subtle; the creature plays at an orderly form, but prefers a coagulation of shapes and consistencies that drive the mind mad with primal fear. It is at once a devilish impostor and a polymorphic mass of flesh and terror.
Clearly, this is an homage to John Carpenter’s The Thing, but it could apply to so many awful creatures…
Medium aberration, chaotic evil
Armor Class 16
Hit Points 153 (18d8 + 54)
Speed 35 ft.
STR: 18 (+4) DEX: 15 (+1) CON: 17 (+3) INT: 12 (+1) WIS: 11 (+0) CHA: 2 (-4)
Skills Deception -2, Stealth +7, Perception +6
Damage Resistances bludgeoning
Condition Immunities charmed, frightened, paralyzed, petrified, prone, restrained
Senses darkvision 120 ft., passive perception 16
Languages can speak any language with rudimentary ability after 1 minute of exposure
Challenge 7 (2,900 XP)
Amorphous. The formless horror can move through a space as narrow as 1 inch without squeezing.
Boundless Predator. The formless horror can spend its bonus action to subtly change its form to gain a swim, fly, climb or burrow speed. This movement type lasts until dismissed. The formless horror can only have one additional movement type at a time.
Inspire Terror. The formless horror can use its action to transmute itself superficially. It can retain its shape or take a new shape as normal, but it augments that shape with disgusting appendages, teeth, and other putrid features that inspire terror in all those that witness it. Any creature within 100 feet that can see the formless horror must make a DC 16 Wisdom saving throw or become frightened for 1d8 rounds and take 14 (3d8) psychic damage. Creatures that success on this saving throw take half as much psychic damage and are not frightened. Creatures frightened by this ability must make a saving throw at the end of each turn, ending the frightened condition on a successful save.
Mimicry. The formless horror can take the shape of anyone and anything by using an action to take that form. When taking the form of an object, it is indistinguishable from an ordinary object as long as it does not move.When taking the form of a living creature, its disguise is less thorough, but it is still difficult to pierce. The formless horror is always considered to have rolled a natural 20 on its Charisma (Deception) check against active or passive attempts to see through its disguise.
Multiattack. The formless horror makes two appendage attacks.
Appendage. Melee Weapon Attack:+7 to hit, reach 10 ft., one target. Hit: 22 (4d8 + 4) damage. The creature can choose from the following damage types; acid, bludgeoning, slashing, piercing, and poison damage.
Shock Attack. The formless horror can use its reaction to attack a creature that is within 10 feet while the creature in the form of an object or a perceived ally. This attack deals an additional 14 (3d8) damage as chosen by the formless horror (see appendage attack), and deals 14 (3d8) psychic damage to any ally of the target within 30 feet of target.
Alternate Formless Horror
As an alternative to the formless horror above, you can remove its amorphous and mimicry abilities, as well as its ability to deal poison or acid damage, and instead give it the following feature.
Head Parasite. The formless horror’s natural form is that of a worm that crawls into the bodies of humanoids, seeking to take the place of the victim’s head. Victims must make a DC 14 Constitution saving throw, becoming killed and becoming a new host for the creature’s second life cycle stage.
The formless horror can then shape the head into various deadly forms to kill and consume flesh. When not actively hunting prey, the creature is indistinguishable from the humanoid that it infected. If the creature’s hose body is killed, but the host body is intact, it can attempt to usurp another body by decapitating a new host and simply inserting its body into the stump. The parasite can eventually evolve by transmuting the entire host body into a deadly mass of flesh, then budding off new parasites to infect new hosts.