Unending Nightmare (5e Creature)
From D&D Wiki
Medium celestial, chaotic evil
Damage Resistances bludgeoning, piercing, and slashing from non magical weapons
Sense Magic. At all times the sandman senses magic within 120 feet of it. Powerful or continuous uses of magic (as well as large, magical locales) can be detected from even greater ranges (at DM's discretion).
Astride Two Realms. The sandman can enter the Dream from the material world, and vice versa. It is visible in the material world while it is in the Verge of Dreams, and vise versa, yet it can't affect or be affected by anything on the other plane. when standing on The Verge, the sandman can see into both the material realm and into The Dream. While in The Verge, the sandman can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.
Temporal Displacement. A creature has disadvantage on attack rolls against the unending nightmare unless it also has temporal displacement.
In addition, the unending nightmare has advantage on Dexterity saving throws, unless the source of the effect also has temporal displacement.
Lashing Sands. Melee Spell Attack: +8 to hit, reach 5 ft., one target. Hit: 21 (4d8 + 3) psychic damage.
Terrible Scrutiny. Each creature within 60 feet of the unending nightmare that can see it must succeed on a DC 17 Wisdom saving throw or be frightened for 1 minute. A frightened target can repeat the saving throw at the end of each of its turns, ending the frightened condition on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to this unending nightmare's terrible scrutiny for the next 24 hours.
Soporific Clouds. The unending nightmare creates an impenetrable, shifting mist in a 20 foot radius around itself. The mists last for 1 minute unless the sandman dismisses it earlier. Any creature in or entering the soporific clouds must succeed on a DC 17 Constitution saving throw or fall unconscious until 1 minute passes, the sleeper takes damage, or someone uses an action to shake or slap the sleeper awake. If a target's saving throw is successful or the effect ends for it, the target is immune to the sleep effect of the soporific clouds for the next 24 hours.
Temporal Stasis (Recharge 5-6). A creature that hits the time-tortured with a melee weapon attack must make a DC 17 Constitution saving throw. On a failed save, time ceases to flow for that creature: it is effectively petrified and is also immune to all further damage and conditions.
The stasis persists until removed with a dispel magic spell: the stasis effect is considered to be an 8th level spell. A freedom of movement spell cast on the target will also end the effect.
The unending nightmare can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The unending nightmare regains spent legendary actions at the start of its turn.
Slip. The unending nightmare moves half its speed.
The unending nightmare is a time-tortured sandman. The The Verge of Dreams is a place of ambiguous space and time through which sandmen must navigate to perform their duties. There are dimensional nodes formed from nightmares that seem to last forever, where time is a morass; and rare dread places where horrific dreams are traps of looped time. When a careless sandman fails to steer clear, it emerges as a unending nightmare, having experienced an eternity of tormentous hallucination.