I am a GM searching for some means (spell, magic item, artefact, etc) of replicating the power granted by the notorious Infinity Gauntlet as depicted in Marvel's Cinematic Universe. The effect I'm searching for in the game I am going to run as GM isn't "demicide" but is (if anyone recognises my name and will be in my game spoiler below):

targeting 100% of certain species in the world where my game is set with something like the 6th level spell "Disintegrate".

The 9th Level Spell "Wish" does not seem to suffice due to this clause in the rules for "Wish":

You might be able to achieve something beyond the scope of the above examples. State your wish to the DM as precisely as possible. The DM has great latitude in ruling what occurs in such an instance; the greater the wish, the greater the likelihood that something goes wrong.

Emphasis added.

I'm looking for something reliable, not a monkey paw that Wish seems to function as when anyone attempts to use it for effects of this scope.

Something that ties into established D&D lore rather than "oh yeah, it's like the movie, but in D&D".

If there is nothing even remotely like the Infinity Gauntlet in any official D&D 5e material, or Unearthed Arcana, then are there any official rules or guidelines on expanding the scope of a spell like Disintegrate to target massively large numbers of targets? I could extrapolate from there.

CLARIFICATION: it doesn't have to have "collect sub-components" as the Infinity Gauntlet needed Infinity Stones to be collected from all over the universe. The important part is if there is already anything or anyone in DnD5e official that has such power.

The closest thing I can think of is the Maze Engine

In the dnd5e module Out of the Abyss it says the Maze Engine is...

a mechanical, magically powered device capable of altering reality. Modrons refer to the device as an Orderer because it was designed is to bring order to chaos.

In the campaign itself the Engine is

damaged, irreparable, and precariously balanced above a river of lava, severely limiting its usefulness,

but it could work as a plot element.

Some of the listed effects are

• The engine emits a flash of golden light. All magic items within 300 feet of the engine are destroyed, except for artifacts, which are cast into the Astral Plane.
  


• The engine emits a bright flash of white light. All player characters are transported back in time, as they are now, to the moment when the adventure began.
  


• The hollow interior of the engine flickers with crimson light until the end of its turn, whereupon one dead character or NPC of the DM's choice is restored to life, as though subjected to a resurrection spell.
  


• The engine emits a flash of green light. Each creature in direct contact with the engine must succeed on a DC 18 Constitution saving throw or take 10d6+40 force damage. If this damage reduces the target to 0 hit points, it is disintegrated.

Given the nature of these effects, one could imagine (and a GM could decide) that a working Engine could accomplish what you want.

The closest would be: The Infinity Gauntlet

Its your world - if you need an Infinity Gauntlet, make an Infinity Gauntlet.

It would clearly be an artifact so you can look to existing artifacts for inspiration starting on p.219 of the DMG but you can give an artifact whatever powers you want:

An artifact is a unique magic item of tremendous power,
with its own origin and history. An artifact might have
been created by gods or mortals of awesome power.
It could have been created in the midst of a crisis that
threatened a kingdom, a world, or the entire multiverse,
and carry the weight of that pivotal moment in hi story.

Some artifacts appear when they are needed most.
For others, the reverse is true; when discovered, the
world trembles at the ramifications of the find .

The closest thing I am aware of from anything even tangentially-related to D&D is from Rich Burlew’s vaguely-D&D-3.5e-inspired comic, Order of the Stick. In that,

Vaarsuvius agrees to an infernal deal in order to save their family from a black dragon whose child V had killed in an earlier arc. Hell’s side of the bargain is a “soul splice,” which isn’t actually a thing in D&D, giving V the power of three of the most powerful spellcasters whose soul found their way to Hell. They save V’s family by casting one of the soul’s signature spell, familicide, on the dragon, killing her and her entire bloodline, ancestors and descendants.

That spell also doesn’t exist in any D&D canon, but as an epic spell in a world loosely based on 3.5e, it would have used 3.5e’s “Epic Spellcasting” system, an open-ended system wherein custom spells of immense power could be built—making this a plausible spell in that system even if it was never actually printed in a book. Epic spells are more powerful than 9th-level spells, and so would supersede wish. However, since Epic Spellcasting is irretrievably broken, it is very unlikely that D&D 5e will ever implement it or anything like it.

So something as powerful as described would not be possible in D&D 5e outside of divine intervention or an extremely generous wish.

Great thing about DnD is that you, as the DM, can do whatever you want.

I'm assuming, of course, that you don't want to be cheesy and state "This BBEG Wishes for something terrible and is lucky enough for it to work".

But nothing stops you from creating a legendary magic device (let's say a gauntlet) that allows the user to cast a "Perfect Wish" free of the limitations the Wish spell usually has.

There's nothing exactly like this in 5th edition

There's nothing in any D&D 5th edition product that will give a player character this sort of unlimited power in a reliable way. Wish can't do it, Divine Intervention can't do it, and even lesser deities like Tiamat don't canonically have any way to do it. That suggests you'd need at least a greater deity, but in 5e they don't interfere with the world.

• If someone in the world still has a D&D 3e era epic spell, that could do it. Rain of Fire, for example, will kill just about everybody within a 2 mile radius, and you could make a more powerful version with specific parameters. You normally need to be more skilled with magic than a human can normally get in 5th edition in order to cast one of these.


• Releasing a sealed elder evil or entity of primal destruction like Tharizdun is within the ability of a D&D character, and Tharizdun is canonically defined in D&D 5e, although his exact powers of destruction are perhaps less defined in 5e. The drawback is that Tharizdun is likely to destroy everything. Kyuss, the Worm that Walks, will kill all humanoid life but at least allow undead to survive.


• A disease or plague might wipe out all of a certain race or the people in a certain geographic area.


• I think this answer is the best. When you're the DM, you aren't limited to what's in the sourcebooks like players are.