|Here's the picture that inspired this monster. It is an album cover.|
The dream-shade is a shadow of someone's dream, made manifest in the material world. It appears as a tall, smoky figure whose slender limbs bend and ripple in a growing wind. Dark and shadowy as they are, their sight causes all other colors to hideously brighten and distort, only emphasizing the black figure itself... and the darkness creeping in at the edges of the observer's vision. Everything is soundless, except the howling of winds.
The mere sight of one implants itself in the viewer's mind, such that a new dream-shade haunts their dreams ever after, manifesting somewhere in the world while the afflicted creature sleeps and watches. The one you see now is, in fact, being dreamed by someone thrashing in their restless sleep, perhaps continents away - perhaps in the next town over.
Thankfully, dream-shades are not inherently hostile, though protracted observation seems to irritate them and cause them to approach menacingly. However, they are as slow as if they walked against a howling gale, and can easily be fled.
They are supremely difficult to hit, bending and snapping like a flag on a pole whenever weapons are swung at them. Even on a successful hit, a dream-shade is not truly material: they cannot normally be harmed by stuff of this world - it passes through their smoky form without making any discernible impact. Only magics or the heavenly radiance of silver have a strong effect, cutting through the murk of a dream-shade like sunbeams through cloud-gaps, with severed appendages disintegrating like fumes in a gale.
Their own touch is potentially devastating, parting flesh cleanly and painlessly right down to the bone.
Even if one sees a dream-shade and then slays it, their sleep will forever be haunted, unless the shade that their dreams spawn is in turn destroyed as they sleep. Blacking out drunk alleviates this each night, but carries its own risks. Certain exorcistic magics can cure the problem permanently, though it is unclear whether this prevents the dream-shade from ever again manifesting, or merely casts it free into its own permanent existence.
5E stat block below.
Medium fey, chaotic neutral
Armor Class 18 (preternaturally evasive)
Hit Points 35 (10d8-10)
Speed 20 ft., climb 15 ft.
STR 11 (+0)
DEX 19 (+4)
CON 9 (-1)
INT 8 (-1)
WIS 12 (+1)
CHA 17 (+3)
Saves Dexterity +7, Wisdom +4
Damage Resistances cold, fire, lightning, necrotic, thunder
Damage Immunities acid, poison, and all damage from non-magical or non-silvered weapons
Damage Vulnerabilities radiant
Condition Immunities all, except incapacitated, prone, and restrained
Senses truesight 30 ft., passive Perception 11
Languages none (does not speak or respond to language)
Challenge 4 (1,100 XP)
Dream-Contagion. When a creature first sights a dream-shade, they must immediately make a DC 14 Wisdom saving throw. On failure, the affected creature sees a dream-shade whenever they dream, causing them to have restless sleep and begin the next day with one less hit die available than normal. This condition can be combated by becoming blackout drunk the night before, but this carries its own dangers. This condition can only be cured by Remove Curse, or by the destruction of the dream-shade that these dreams create.
Multiattack. The dream-shade makes two tendril attacks.
Shadowy tendril. Melee Weapon Attack: +7 to hit, reach 10 ft., one target.
Hit: 9 (1d10+4) slashing damage, plus 7 (1d8+3) psychic damage.
Nota bene to DMs: do not be afraid to have "low-level" parties encounter this creature, even down to level 1s. They are not initially hostile, and even if the situation DOES escalate, a smart party can flee when they see their weapons have little effect (...only to find the danger remains, dwelling within their own heads when they sleep!).
Go forth, Reader, and use this monster if you wish. Let me know how it goes if you do!
(If you convert it to another system and I like what you did, I'll make sure to link to it!)