Antimodrons

Modrons don't have a morality like we do.  They have a prescribed set of behaviors, and many rules they must follow.  But desire is never in question--all modrons want to follow the rules, as certainly as humans want to breath air.

But modrons have sins, just as humans have sins.  They only have one type of sin: error.  This can be error in behavior (such as overcharging interest) or it can be error in calculation (such as getting the wrong answer when calculating a 15% tip).  

In the eyes of modrons, both of these are moral failings, and both put a modron's soul in peril of damnation.

Modrons in Hell

Most modrons who are sent to hell become part of the architecture, in one way or another.  It suits them better.

A few modron souls who are deviant enough and tenacious enough to thrive in Hell's soul-churn of debt and predation can rise to become demons in their own rights.

Modronic demons still preserve many of the classic modron traits.  They tend towards simple geometric shapes.  They have hyper-rational minds (although they are not especially intelligent).  And they have have prescribed codes of behavior--although in the absence of the Primus, these modrons must invent their own "Primus" in order to avoid going (more) insane, although I will point out that an insane modron is still more sane than your average human.  

Does anyone know the illustrator?
I think it's from the Monstrous Compendium - Mystara Appendix (2e)

Flying Hole

Lvl 1  (HP 4)  Def none  Consume
Fly slow  Int low  Dis hungry

Voidstuff - immune to all damage except holy damage.  Other spell effects work normally, but the strange minds and senses (see below) must be taken into consideration (e.g. hypnotic pattern does nothing, since they are blind).

Less of a creature and more of an environmental hazard (like green slime), flying holes are the remains of monodrone souls.  They resemble black blots in space, about 2' across.  

They sit motionless for thousands of years, or patrol corridors in repetitive patterns.  They have poor senses, and can sense heat but nothing else, and only in a range of 30' (although larger heat sources can be sensed from further away).  If they ever sense the sun, they will attempt to fly into it, where they are presumably destroyed themselves, the sun being an even greater source of annihilation.

They seek to devour the living, and when they sense a warm-blooded creature near them, they will charge it, dealing 1d20 damage on a hit against a resisting target.  Against an immobilized target, they will fly through the center of mass, leaving a hole 2' wide.

In fact, anything they touch is devoured.  A flying hole can fly right through a wall and leave a perfect hole 2' across.  

They can be distracted by torches with a 5-in-6 chance the first time you use the trick, but this decreases to a 3-in-6 chance the second time, and finally bottoms out on a 1-in-6 chance from the third time onwards.  They are not mindless, and they will learn.

Devoured matter has different fates, depending on its substance.

• Natural, inert matter phases back in after 1d6 exploration turns.
• Crafted, inert matter phases back in after 1d6 exploration turns completely repaired.  Bent swords are repaired, broken locks are fixed.  Flying Holes are incredibly good at this task, and sometimes you can get one to repair obtuse ancient mechanisms, or to fill in blank spots in water-damaged scrolls.  They are not infallible at this task, though.  (This ability is not well known, and is poorly understood.)
• Living matter is eaten.  Flesh and blood are physical digested.  Indigestible bits such as bones will simply fall out of the bottom of the flying hole once digestion is complete.

If devoured matter is still semi-anchored to a physical location, it will return "in-place".  A hole in the wall will fill itself back in, leaving the wall exactly as it was (although any cracks in the plaster will be repaired).

If devoured matter is not anchored, it will fall out of the bottom of the flying hole once "digestion" is complete.

Discussion

Spheres of annihilation / blackballs / umbral blots are much too interesting to be used only at high level. 

They work well at low level play, where the game tends to be about learning to exploit your environment.  And flying holes are certainly exploitable!  You can use them to cut holes through stone walls, trick them into destroying your enemies--but only at considerable risk to yourselves.

One of my philosphies is "nothing is mindless".  I don't like seeing how D&D has reduced most complex interactions (familiars, summons, warlock patrons, intelligent weapons, reaction rolls) into programmatic mechanics.  Too many things are mindless in D&D.

I try to extend this to elementals, golems, and all forms of undeath.

Can you make a flying hole angry?  Of course!  That makes the game better.

Behond the Takara Tomy Amaterios Evil God WBBA Beyblade Burst Evolution Wheel / Layer B-00, which is actually has some good names inside it for a demonic lich top.

Black Metal Murder Top

Lvl 3  (HP 10)  Def chain  Beyblade

Mov fast  Dis hungry

Black metal and modronium blades, wrapped in pull-chains, resting in the hollow abdomen of a large skeleton.

Fel Momentum - Demon tops cannot be truly destroyed except in a smelter.  In combat, their HP represents their rotational momentum--how fast they are spinning.  Demon tops can jump up to 2', but it costs them 1 HP to do so, and they can only jump once per round.  They also lose 1 HP every round, just from spinning.  Things that impede their spinning (sand, clutter) increase this HP/rnd cost.

Whenever they are missed with a slashing or bludgeoning attack, they convert it into momentum, gaining 2 HP.  (It doesn't matter if you swing at them from the opposite direction--they are able to reverse their spin like a rattleback.)

Beyblade - A demon top deals 1dX damage, where X is equal to their current HP, rounded up to the nearest 2.  For example, a demon top with 7 HP deals 1d8 damage on a hit.

Necromancer - Every demon top is a necromancer, capable of raising and controlling lower-level undead.  They typically ride in the stomachs of undead that they have dominated in this way.  They use their dominated undead to yank their chains, sending them flying into battle.  Their listed HP of 10 represents an average corpse.  Stronger corpses can send them into battle with greater momentum (HP).

Even at 0 HP, a demon top is capable of calling to undead from across the dungeon.  Lesser undead will seek out the demon top and start carrying it around again.

They are capable of speaking with low, buzzing voices.  They are the remains of tridrones.

Discussion

Black Metal Murder Tops are meant to be alternatives to liches in low-level undead dungeons.

It might arrive at the head of half a dozen zombies, barking orders from the belly of the biggest skeleton.  

Even if you kill the zombies and arrest the demon top, it is still difficult to destroy it.  The players can try to throw it down a hole or something, but sufficient numbers of undead are capable of retrieving their master from most places.

If you remove the demon top from the dungeon, it will continually attempt to strike bargains with you, while summoning undead to your location.  It doesn't fear destruction, since you'll have a difficult time destroying it without an active volcano, dragonfire, or a full-scale smelter.  (Your local blacksmith's kiln doesn't cut it.)

They're meant to be the solo boss of a low-level necromancer dungeon, but you can certainly use them in groups.  If you do so, they are capable of stealing spin* from each other as form of HP vampirism.

*if you've never dug into beyblade lore, it's wild.  e.g. Moses used his beyblade to part the Red Sea.