Nightwalker (MToF)
Nightwalkers are categorized as undead, but perhaps it would be better to think of them as anti-life elementals from the Plane of Negative Energy. Nightwalkers themselves are basically walking fields of death that only exist to kill everything. It is implied that they share a superficial connection to whomever freed them from the Negative Energy Plane, in so far as they gravitate towards areas that said creature had a connection too. But other than that, they have no true personality or even a culture.
Instead, we are going to talk about D&D metaphysics for a bit, because that’s actually relevant to this creature. As you may or may not know, the Multiverce is the default D&D setting. And the Multiverse consists of a series of planes arranged in a peculiar order. You can see pictures of this order in the DMG. It is implied that the other planes surround the Material Plane, where most adventures and campaign settings reside. It’s complicated, mostly due to the fact that we aren’t talking about 3d space here, it’s more like 6d or 7d space with all the directions you can go. And it is further complicated by the mutable nature of planes. Fortunately for this discussion, we can toss out a lot of it and start summarizing the key bits with this picture here:
Basically, the Positive and Negative Energy Planes have their own axis. If you travel from the Material Plane (which is in the middle of that ring of Outer Planes) to the Positive, you will end up traveling through the Feywild. Likewise to get to the Negative, you will have to go through the Shadowfell.
People can travel to the Negative Plane for various reasons, but mostly it’s just the unscrupulous search of power that draws people in. Once a person gets to the Negative Plane, the Negative spits out a Nightwalker to fill the metaphysical void from their missing presence. Afterwards, the creature that traveled to the Negative is trapped, unless someone can trick the Nightwalker to go back into the Negative, to take their place. Simply destroying the Nightwalker is not an option, as that will imprison the creature forever.
Honestly, I wouldn’t be surprised to see this lore used for a Stranger Things season.
In combat, the Nightwalker has better than average speed, including a flight speed. It attacks by flinging around a lot of negative energy in the form of necrotic damage. Simply standing next to it will damage someone, its melee attacks can prevent healing, and it has an extreme ranged attack (albeit one on a cooldown) where it points at a target to damage, scare, and paralyze them. Finally, any creature killed by them can’t be resurrected, except by a Wish.
I dare say this monster is too complicated for its intended simplicity. Does it truly need to inflict fear and paralysis at the same time? Why the 6 recharge on its only ranged attack? It’s not like a breath weapon or anything, it’s just pointing a finger. And finally, at cr 20, do we really need a CON save to avoid the HP reduction of its melee attack? Just slap on a
Greater Restoration clause and have it automatically apply. The real challenge here, of course, is not killing the sack of HP before you can shove it back into the Negative Plane.
In the changeover, the Nightwalker had its HP buffed by a bit. The damage rolls on its aura and Finger of Doom were likewise raised, however it lost the Advantage granted by the Annihilating Aura in the process.