Gelatinous Cube, Ghost

AD&D Gelatinous Cube
These monsters are hilarious. Rather than a blob of killer goo, they're a cube! A cube! Amazing. So amazing that it is often forgotten, especially in art, that they're supposed to be nigh-invisible, which would definitely detract from all the art of adventurers battling a jello cube, so I can hardly complain. Unlike most oozes, they are not particularly difficult to kill, as normal weapons can chop them up without issue, as can fire (though personally I find it unlikely that a flask of burning oil could meaningfully affect that much protoplasm without simply being extinguished as the ooze advanced).  Cold halves their damage and move but does not kill them, so they could probably survive being frozen solid.

They paralyze for 5d4 rounds upon hit, and deal a respectable 2d4 damage, but with a low AC, movespeed, and 4HD, they just aren't a big threat to an actual party of adventurers, but with the paralysis and surprise chance of 1-3, they have decent odds of picking off scouting thieves, wizards hanging in the back unaware that a Cube is after the party, and people the dice hates. As such I think they are most effective as complications to other encounters than encounters in their own right, and could be re-imagined, statistics wise, to be more of a 'crushing wall' to avoid being trapped by and escape, than a soft jello blob to chop up.

The most amusing feature of the cube is the treasure suspended in them- this can be used to occasional puzzling effect when you describe a suit of armor suspended within a cube floating statically forward in dim dungeon lighting, or a sword, or assorted jewels. I think the minor treasures found within cubes can be more interesting if the players must come up with a plan to fish them out without being eaten, rather than simply as the reward for beating these relatively feeble monsters like a pinata.


AD&D Ghost
I think it is interesting that ghosts are not simply any old spirit, but specifically people who were so evil they were cursed (or rewarded) with their undead status. So the statblock is not for the common concept of 'ghost as soul that has not moved on' with tragic overtones or unfinished business, no, it's just some asshole hanging around long past their expiration date.

They cause fear and aging on sight, with clerics of level 6+ being immune, and are not merely protected by 'can only be hit by magic weapons' but are actually properly on the ethereal plane, just also happening to be coterminously visible. They can possess people who get too close, and if this fails, they can semi-materialize to strike for 10-40 years of aging in melee, at which point they can be smote with silver for half damage or magic weapons for full, though with 10HD and AC0 (or 20 for ascending AC) this seems likely to be a pyrrhic victory at best thanks to the aging.  Most perilously of all, perhaps, they cannot be struck by spells unless the caster has entered the ethereal plane along with the ghost (if those wishing to battle the ghost venture there, they will find its AC is 8 points worse). Any of the original player races except half-orcs slain by a ghost is forever dead, though half-orc immunity might be an oversight rather than deep lore.

Unlike some other undead, they have no particular weaknesses (even outwitting-wise they are said to be of 'high' intelligence), though it may be worth mentioning there is no mention of flight or swimming capabilities, so deep water or flight might be a way to escape from them. They also are 'Lawful Evil' which might indicate some possibility that they are bound by certain rules, or authority from whoever or whatever cursed/blessed them to their unholy might in the first place.

Finally, they have treasure type E and S, which has pretty good odds of potions and probably one decent score of treasure (with low odds of getting absolute heaps of loot). This is probably a mix of their own grave goods and that of their victims.

Sunset Realm Gelatinous Cube
Considerably more solid than other oozes, they mostly devour algae and mold from dungeon walls, and as such take on the general shape of hallways, and so come in alternate shapes such as gelatinous domes (for arched ceilings) and other such things. Their paralysis is not chemical, but physical- those who are "paralyzed" are just sucked into the body of the creature and held immobile and helpless by hundreds of pounds of stiff, corrosive gelatin until they suffocate or are reduced to a skeleton.

They are among the most 'domestic' of oozes, though they are far from tame. However, dungeon dwellers, most notably deep-dwelling fortress dwarves, sometimes use them as cleaners/pest control/garbage collection, for they are harmless to inorganic materials and as such good for cleaning places composed entirely of stone and metal. When such 'Cleaner' slime are used in inhabited areas rather than unstaffed areas, they are typically pruned to be gelatinous rectangular prisms, as this does not affect their cleaning abilities, but prevents them from engulfing and suffocating people if they are only a foot thick.

As a minor aside, the gambling god of chaos T'liki inscribes runes on the sides of these creatures so that they may roll about like dice and cause magical mayhem, and T'liki may set these creatures on those he is wrothful with (or happy with, T'liki is not very consistent), with the most terrible manifestation being the 20HD, 20-sided Gelatinous Icosahedron...

I didn't draw this specifically for this post but I haven't posted in like a month, corners must be cut

Sunset Realm Ghost

Life is sometimes described as 'A ghost riding a skeleton wearing a meat suit' but this is not quite true.
A ghost is a particular manifestation of a spirit or soul, affecting the physical world by virtue of possessing base elements that are human enough to be valid possession targets without requiring massive spiritual strength to dominate the elemental souls within all things. The dust of flaky skin, the moisture of sweat, exhaled breaths- it is these fragile, scavenged pieces of humanity a ghost uses to cross over from powerless soul in the afterlives/dream realm to manifested ghost in the waking world. It is easiest to do this with scraps of one's own decaying body or the detritus of a relative (indeed, most ghosts are simply those lurking around their own unburied corpse, unable to bear the pain of reanimating it themselves, but wanting to get others attention so that they may be properly buried), but with enough determination, a ghost can manifest with even the dust of old trees and spiderwebs.

Ghosts are essentially as they were in life, for good or ill, and cannot be permanently exorcised by merely scattering their incorporeal bodies- so long as their will to remain remains, they can construct a new body without much issue- magical weapons drive them off in the dream realm as well as the waking world (usually until next nightfall) and are useful for buying time, but are not permanent solutions. As such, exorcisms are more akin to therapy and crime investigation than ghostbusting. One must determine why a ghost is lingering about, which is often difficult due to language issues, physical communication issues from less-physically-coherent ghosts, and of course, any danger posed by a wrathful or frustrated spirit which can call down all manner of tricks from when it was alive. Furthermore, by default, elemental wrath in the form of aging is a threat from frustrated ghosts, as ghosts may, intentionally or otherwise, rouse the minor elementals within things to try to destroy a perceived unlife violation of the elemental covenant which allows souls to inhabit matter, and get the living caught up in it due to collateral damage expected of elementals that are literally dumb as rocks, airheads, or... wet behind the ears? (If anyone has a better water-based phrase implying bad judgement/low braininess do tell me)
The other prime threat of a ghost is possession- compared to microscopic particles, an entire body is MUCH easier to take control of and has many benefits. Those who are body-snatched may stay in their body and try to wrest control back for brief moments, or they may wander as ghosts themselves, typically with a bit of a learning period. While charms to prevent this are not entirely uncommon (any priest or witch worth their salt should be able to make one, the level 1 spell Protection from Evil will do), vigilance with regards to constantly checking that the charm is not lost or damaged must be kept!

Some ghosts trauma is so great that they are semi-or-entirely trapped in a Nightmare Realm, unable to perceive reality as it truly is and reliving the horror of their death (or life) and dragging others into it. This can manifest as full entry into an alternate reality, or aspects of the trauma manifesting into reality (ie, a ghost who burned to death might be a pyrokinetic). These ghosts are the ones that blur the line between 'person who happens to be noncorporeal' and 'monster,' but 9/10 exorcists agree that a ghost that still has its original form is still a person who can be helped- if the psyche collapses and the soul flees not only the waking world, but the dream world/afterlives, the remaining thing is a Wraith, an anthropomorphized Nightmare Realm, and no longer the original person.


Ghost-On-The Go
So you rolled 'Ghost' on someone elses encounter table and feel a 10HD AD&D murder-happy ghost just isn't quite what you want to spring on the party.

Ghost Motives (d6)
1-2- Improper Burial. The ghost's body or grave is desecrated, or they need to be buried in a proper graveyard with their ancestors/friends, something like that. These ghosts are the most common as while the details of how they ended up like this can be wildly variable, their basic desire is the same.
3-Escapism- The ghost has grown tired of afterlife shenanigans and wants a vacation in the waking world. They will prioritize possession, hedonism, and spectacle. Typically, psychopomp spirits/exorcists will arrive to put a stop to these shenanigans sooner or later, preventing long-term bodysnatching, but if not, the best course of action is to find out what the ghost is really trying to distract itself from in its afterlife, and find a way to address that, rather than simply guiding it on the least-destructive bender and hoping for the best.
4- Injustice- The ghost was wronged in life- murdered, abused, betrayed, and so on, and can't move on until they are satisfied wrongs have been righted. The less justice-motivated ghosts are just in it for vengeance, morality be damned, but cannot rise as corporeal revenants and do it themselves for some reason. Either way, these ghosts tend to be emotionally driven and prone to excess, but can oft be sated by symbolic satisfaction in the event the injustice cannot be properly solved due to the march of years.
5- Unfinished Business- The ghost needs to do something not for itself, but for someone yet living- confess love to an old friend so they can move on, find the True Heir to the throne, save their family farm from tax collectors, etc etc. As this ghost requires material results rather than emotional satisfaction, they tend to be more grounded but also more picky.
6- Madness- This ghost suffered so intensely or for so long that direct contact is too dangerous to allow for proper communication.  Reroll a d4+1 to determine motive, but this motive cannot be learned from the incoherent, inconsolable ghost itself and requires serious, in-depth sleuthing to figure out how to perform an exorcism.

Ghost Powers
1- Poltergeist- The ghost has trained itself to be able to move objects, usually violently, but more subtle behaviors like untying ropes or locking/unlocking doors is possible too.
2- Thematic Powers- Based on their life or death, the ghost might be able to manifest either real or ectoplasmic events that mimic their own experiences- ie, a ghost who was a dog trainer/eaten by wolves might be able to summon wolf packs, or drive dogs mad, or just summon ectoplasmic canines to chase the players with.
3-Cold Spots- Light and heat are coveted by the dream realm, and the bridge between it and the waking world allows for the leeching of energy. The ghost can freeze liquids, bring rooms to freezing temperatures, and cause touched things to frost over.
4-Omnipresence- The ghost haunts an entire thematically appropriate area, and can dimly sense all that occurs within the haunted area, as well as teleport about with ease.
5-Nightmarish- The ghost has become twisted from trauma and isolation, and corrupts the surroundings with a Nightmare Realm (see The Nightmares Underneath, free edition. Or expensive edition if you have it, I suppose)
6-Wizard!- Becoming a spirit did not break the connection this wizard had to their spellwisps, and indeed, being on the same plane as their strange spellwisps, demons, and so on may have even strengthened their connection. Spellcasting Wizard-Ghosts who intentionally achieved this state of being are typically referred to as 'Spectres,' and are perhaps even more annoying than their corporeal counterpart of the Lich.

Rewards of Exorcism
1- The appropriate god or necropolis the ghost should've been resting peacefully within is grateful, gain +1 favor (or clear Wrath) with the appropriate spiritual entity, or increase your Luck score by 1, DCC style.
2- Ghost decides to hang around a little longer and can be learned as a spell by players if the appropriate gold-prices are paid (A lumberjack ghost being a spell to 'Fell Tree,' for instance).
3-Ghost answers questions the players might have about local events, rumors, etc, paying them with information it gained while it was dead.
4-Ghost owes them a favor, can return once to do ghosty things in the future to aid them (and will do so to rescue them if they are in peril and forget their ghost favor).
5- Word of party's ghostbusting spreads, giving them +1 to local reaction rolls from townsfolk and so on, and perhaps eventually leading some manner of exorcist to get in contact with them about thrilling multiclass opportunities.
6-Ghost reveals locale of treasure hoard (as treasure map), understanding that the players, as material beings, could probably use material compensation.