Atropus

That's no moon...

Atropus, the World Born Dead is an undead Primordial and Elder Evil who also happens to be an entire moon. Said to be as old as creation, this sentient celestial body goes around destroying planets since it has a hate boner for all life. Not even the gods can kill this thing, so all adventurers can really do against it is attempt to shoo it away before it plunges into their world and drains it of its positive energy. The most likely way of doing that is killing the Aspect of Atropus, but that requires venturing onto the undead-ridden surface of Atropus and finding it, and that's no small task. It is also the polar opposite of a different Elder Evil, Ragnorra.

Atropus is also speculateed to either be the first Atropal or their source/creator, based on their similar names and origins - both are undead abominations that are said to be stillborn immortals.

In terms of crunch, Atropus itself has no stats (because let's face it, if the gods can't fight this thing head on neither can you) but its Aspect is a high-challenge Gargantuan Undead that'll really only be seen as the final boss of a campaign featuring the undead moon.

Where the fuck did it come from?

While origins can vary between settings, all depictions have Atropus being as old as time - essentially being described as a primal force of undeath that exists only to create more undead and snuff out all life.

In the Forgotten Realms specifically, scholars believed that the World Born Dead was accidentally created by Ao, either indirectly as a byproduct of the creation of the first god of death, or directly as a divine mistake - the last god created, stillborn in immortal undeath upon creation. However, both of these origin theories conflict with it being described as a Primordial, so whether Atropus is indeed the fault of Ao or not is up in the air (or up for the DM to decide).

The surface of Atropus

The surface of Atropus is, expectedly, as barren and lifeless as the being itself wants the D&D multiverse to be. Unless its touching the atmosphere of a world that it's about to crash into, there's also no atmosphere, so unless you want to cut it extremely close you'll need some method of breathing up there. The only notable surface features besides Atropus' face is some craters.

Besides the lack of oxygen, the main threat upon Atropus is the legions of undead that inhabit the world, all born of nightmares. These include the aforementioned Atropals, as well as dread wraiths, nightwalkers, angels of decay, nightwings, rage winds, advanced deathshriekers, famine spirits, and the like. There's also a single dread boneyard on Atropus, though why there's only one on an entire planetoid of undeath makes little sense.

Since Atropus is also an Elder Evil a DM may also sprinkle in some Star Spawn and/or make being on Atropus maddening. Either way, be prepared to slaughter hordes of monsters on your way to the head(less) honcho...

The Aspect of Atropus

What you're actually going to fight.

Chances are, finding and slaying this thing is why you even set foot on this abomination. A headless Gargantuan Undead, the Aspect of Atropus is the final obstacle between a party and sending Atropus packing. It's definitely no pushover, and just standing near it is enough to get weakened considerably and take necrotic damage - and attempting melee is suicide anyways, since (depending on the edition) it's entirely immune to nonmagical damage. However, it can't teleport or otherwise force you into the range of its adverse effects, so its entirely possible to cheese it to death by keeping it at range and using all your best spells.

Patronage

Since Atropus is an Elder Evil, some evil Warlocks, Wizards (particularly Necromancers), or Death Domain Clerics (or Ur-priests in older editions), as well as cults, may serve it. Usually these are NPCs or outright villains, but theoretically a player Warlock can take Atropus as a Great Old One patron if the DM allows it. However, someone with Atropus as a patron will more often than not be (chaotic) evil and/or cynical, so unless the reason why someone is worshipping an apocalypse-bringer is tagging along with a group that's usually tasked with saving it is well explained, or the DM has plans to work you into their plot, you'll probably be forced to change patron. You may also be forced to give up control of your character at some point, especially if Atropus itself shows up.

Followers of Atropus (that the World Born Dead is consciously aware of, or have been contacted by a Star Spawn emissary of it) are directed to spread undeath as much as possible, as to prepare their world for the arrival of their master. They will often also seek out artifacts and/or writings that may bestow upon them the knowledge to expedite Atropus' arrival (and/or grab their attention) - though several of these are associated with Allip curses. The only surefire way to get one's hands on a method to call it is to obtain the Book of Vile Darkness.

Follower overlap with Orcus is expected, since both beings have similar goals (the replacement of life with undeath).

How to tell if your DM is using Atropus

Besides the obvious 'someone or some cult is trying to call Atropus to the world', a sign that foretells the coming of Atropus is the undead rising with no other explanation and necromancy becoming more powerful. If this occurs, or you have the suspicion the campaign is leading to an encounter with the World Born Dead, it's best to keep an eye on the night sky (and never the sky in the day, as Atropus always keeps the planet it targets between it and the sun) - if the DM is indeed planning an Atropus encounter chances are you'll spot them, rock-face and all.

External links

• Homebrew 5E stats for the Aspect of Atropus, as well as other Elder Evils. Be warned, they fixed the cheese and its now CR 30.