Tuesday, August 17, 2021

BITTER DRYADS (Brothers/Children of the Pines from the Chronicles of Corum)

The People of the Pines/ Rodney Matthews/ 1977

AC +4 (see below)    HD 4+4 (see below)     Move 100% Normal Human     ML 10 (see below)

Once mortals, the Fomorians poisoned the first with mistleberries and transfused them with the sap of winter pines, making them undead. The Dryads now carry out the ritual themselves, sometimes even persuading the living to join them of their own will - but otherwise by submission.

Bitter Dryads retain their mortal form but skin and hair turns green. Morphic resonance has evergreen leaves and needles, moss, lichens and berry-like growths replace their hair, clothing and personal ornament over time. They bleed green, sticky and slow.

They prefer the shade of the forest, the gloom of winter, and the dark of night, but are not vulnerable to sunlight.

Retaining their intelligence and memories, the Bitter Dryads are the ironic, rustling voice of the  Fomorians in the mortal sphere. They are fully conscious of what they do even as it goes against anything they once loved or believed in their mortal life.

Three blasts of the Horn will strike them as instantly dead as it does the Half-Dead.

The Dryads are inextricably linked (and loyal) to the Fomorians through their weird reptilian steeds.

Dryad Horses are intelligent, capable of subvocal/telepathic communication with their rider and the Fomorians, and serve to direct the Dryads according to that greater will.

It is said that these lizard-things are vomited up by the Fomorians, fully formed extensions of their dire personality.

  • As long as a Dryad is in the presence of their Horse, they are an AC +4 HD 4+4 Invulnerable Monster. If they are mounted, they regenerate 1 hp/round - even from 0 hp - and cannot be Turned. 
    • Treat mount and rider as a single unit/statblock wherever possible/reasonable.
    • A Dryad without a Horse is AC +2 HD 2+2 and normally vulnerable; they also have a -1 Initiative penalty. Morale drops to 8 (or 6 vs. fire). Turned as similar HD undead.
    • A Horse without a Dryad is AC +4 HD 2+2, an Invulnerable Monster and regenerates 1 hp/round. Move without a rider is 200% Normal Human, 150% with an unarmoured or shielded rider, 100% with an armoured rider. It is otherwise mechanically the same as a Bitter Dryad.
  • No armour benefit unless it is better than their base AC. Shield bonus stacks.
  • Can make weapon, missile and unarmed attacks with a Strength of 13 and a Dexterity of 10.
  • Immune to cold, gas, hold, charm, sleep and missiles (inc. magic missile).
  • Save vs. fire at -2 and take +1 damage per die (ML 8 vs. fire).
  • Surprise 1-3 on d6 and undetectable when stationary 1-4 on d6 in evergreen/winter forest.
  • At 0 hp, unless by fire or acid, the Dryad is helpless, not killed, and able only to sense and speak. Even beheading and dismembering cannot silence them.
    • Dryad Horses try to recover their fallen riders.
    • Killing a Dryad's Horse allows the Dryad to be killed with normal damage.


I first encountered the Brothers of the Pine in The Best of White Dwarf Scenarios Vol. II

I hadn't read the Chronicles of Corum at this stage, so they were just a cool monster in their own right. 

I remember being fazed by the '-20% Morale' because I thought Morale was on 2d6 not d%, but assumed it was the kind of shorthand that I'd eventually get to understand. At that stage, I thought of rpgs (and rpgs being mainly D&D) in general being a new thing, rather than something that had been around for 10+ years, and expected there to be a lot more compatibility between them than there was.

I've used the BECMI/OSE Wood Golem as the base monster for both mount and rider. 

The relationship of the Pine People to their mounts was something I'd forgotten about, and I couldn't not include it.

THE HALF-DEAD (Ghoolegh from the Chronicles of Corum)

I have a very strong mental image of what the Ghoolegh look like. This is not it, but this is what I could find.

AC as armour     Move 50% Normal Human     HD 5+5 (hp only)     ML 12 (see below)

Balanced on the very edge of death, their blood runs cold and slow and only at the behest of their Fomorian controllers/creators.

They are death pale with bloody red eyes. They are dull-witted, clumsy and sluggish, but capable of operating devices and independently carrying out orders. Their speech is halting and sombre, without emotion. They dimly remember their mortal life and skills.

The Half-Dead act as handlers to packs of Hounds of the Horn (Fomorian hunting dogs) and may be mounted on Ghoul Horses (unarmoured light warhorse, immunity and attacks as a Ghoul and Horse, will not accept rider with more than light armour & shield; carnivorous, intelligent, disloyal and sly).

They must obey whoever blows/holds the Horn of the Hounds, allowing new saves vs. charms etc. If they do not respond promptly to the first two blasts, the third will instantly slay them.

  • Always loses Initiative/acts last in a combat round.
  • Only defeated when finally cut to pieces or beheaded:
    • On critical and/or 9+ damage hits, they lose a limb. On 12+ damage hits, they lose their head.
  • Attacks as a Normal Human at -1 to Hit, damage bonus of +2 (or as Strength 16).
    • Makes missile attacks as Dexterity 6.
    • Can also make unarmed strikes, grapples and overbearing attacks.
  • Immune to cold and do not breathe, but are otherwise not undead and can't be Turned.
  • The Half Dead are without fear of mortal foe, but fear fire (ML 8), though they can and do use it and are not especially vulnerable to it.
  • When the Horn blows once, they panic, struggling to interpret meaning and respond (ML 6).


I'm genuinely surprised that I can't find more gaming material related to The Chronicles of Corum (Michael Moorcock), though that might be because they (especially the more strongly pseudo-Celtic second part) made such an impression on me rather than any wider merit or need.

In an attempt to fill that gap, here's the Ghoolegh (pronounced however you like) in approximately older edition D&D dress-up. I'll follow up with the Hounds of Kerenos, the Brothers/Children of the Pines, and the Fhoi Myore.

I've used Dragonwarriors Zombies converted to D&D adjacent - all those hit points represent how much punishment they can take. In the books, one still slithers on its belly to attack when all the bones in its body are broken.

If you don't like the cop-out of a big sack of abstract hit points, use regular Zombies or even Normal Humans but make them Invulnerable Monsters.

I've seen the suggestion to use the AD&D Juju Zombie, though I don't think it's a good fit.

THE HOUNDS OF THE HORN (Hounds of Kerenos from the Chronicles of Corum)

Jill Thompson (art)/Ray Murtagh (colour)
From the comic adaptation of The Bull and the Spear

AC +4     HD 4+1     Move 125% Normal Human     Morale 10

Dead white hounds, the size of a pony or a small cow. Blood red ears - sometimes tails, paws and bellies, too. Capable of great leaps in the air and running tirelessly over miles of snow-covered terrain.

They obey the Fomorians as much because they recognise their power as because they are bound to the Horn. The Horn calls and controls them, but does not strike them dead.

  • Bites for 2d4 damage.
    • On a crit or if damage rolled >target HD/level, you're knocked prone (50% drop whatever you're holding)
    • If they hit a prone target, they worry for 2d4 hits per round.
    • If two Hounds both bite the same target, they try to pull them limb-from-limb for 4d4 hits per round; if damage is 12+, they have pulled off a limb and will release the victim to fight over it.
  • If you have 3 HD or less, save vs. fear or flee when attacked by a Hound or Hounds; Morale check to hear their baying in the distance.
  • Immune to cold.
  • They absolutely obey whoever blows/holds the Horn of the Hounds (overriding any other mental control), but can otherwise be directed by anyone able to handle them successfully.
  • For even bigger Hounds, swap d6/d8 HD for a d10 or even a d12. Add one or more d4 to damage or give it a 2d6 bite attack like the Bloodbeast.


White Dwarf no. 18 carries stats for Hounds of Kerenos, pitching them as frosty Hell Hounds - though a Winter Wolf would work just as well.

I've used the BECMI Dire Wolf with a bit of Giant Shrew as the base, but there are various monster hounds and wolves across various games and their editions that would work just as well. 

I think that they're living things rather than magical beasts, which is why I've not given them a breath weapon. They are specifically a reference to the Cwn Annwn, with their white coat and red ears.

Thursday, July 22, 2021

ALLANSIAN BLOODBEAST: Monster Conversion - Fighting Fantasy to Old School

Iain McCaig 1984

Armour Class +4     Hit Dice 7     Move n/a     Morale n/a

Bloated and limbless, it eternally wallows in the pool of slime it was spawned in.

The Allansian Bloodbeast is an Invulnerable Monster and regenerates 3 hp/round from any source. 

It is immune to acid and normal fire. Very hot/large and magical fires (causing 10+ hp damage) cause half damage but it retreats to the bottom of its slime pool for at least 1 combat round.

Electricity causes only 1 point per die, but reduces its attacks by 50% for 1 combat round. It will 50% retreat to the bottom of its slime pool for the duration instead.

Tongue: Its 10' prehensile tongue will grab a victim of size M or smaller and drag them to be bitten or (50%) into the slime pool on the next round. To resist the drag, grapple vs. STR 18.

The tongue can be severed with 6 points of slashing damage in a single round. If this happens, the Bloodbeast retreats to the bottom of its slime pool and will not emerge until the tongue regenerates (1 on d6 on the first day, 1-2 on the second and so on).

Bite: It bites for 2d6 hits. On a 9+, you lose a limb. On a 12, it crushes your skull/bites off your head.

Only those grabbed by the tongue or attempting to attack its weak spot can be bitten.

Slime Pool: If unprotected and susceptible, you must save vs. fumes each round or be nauseated (as Troglodyte stench) and partially blinded (as if trying to avoid a gaze attack). 

On a critical fail, you are overcome and collapse helpless. The Bloodbeast will grab you with its tongue at the next opportunity and drag you into its pool.

Anyone dragged into the slime pool suffers d6 acid damage each round and is unconscious after 2 rounds.

Weak Spot - Real Eyes: The Bloodbeast has hundreds of false eyes that burst from blisters on its head. Its vulnerable real eyes are hidden amongst these.

A crit against the head will hit a real eye (or 5% chance). If the attacker knows the Bloodbeast's weak spot, they can increase their chance to 10% equivalent. If this seems too much of a challenge, apply a -4/20% penalty to hit instead (called shot equivalent).

Striking an eye causes the Bloodbeast to suffer half its HD in damage (3d6+3 or 3d8+4, and instead of weapon damage). It will retreat to the bottom of its slime pool to recover at the next opportunity.


I sometimes forget how awesome the Bloodbeast from Deathtrap Dungeon is/was. 

IIRC correctly, in the gamebook you can't fight it normally and must either get a lucky strike against an eye, sever its tongue or dodge past it. Or die, of course.

It's not a monster you're meant to kill. However, Fighting Fantasy as a setting tends to the lower end of magic weapon allowance so you might need to go the whole hog and make it like some iterations of the Hydra so it can't be killed with body hits alone. Or go the Call of Cthulhu route and reducing it to 0 hp merely drives it the bottom of its pit.

The cover illustration suggests it has a stinger, but this is not mentioned in the gamebook or in Out of the Pit. But it does get used in the Playstation game, in which it also gets to spit poison, use magic, is vulnerable to the Venom Sword, and has only one real eye.

No idea how the Bloodbeast is meant to have evolved or how it breeds or how it even gets about. It seems likely that it secretes its own slime, as it uses it as a pre-digester. 

Maybe that stinger is an ovipositor and implanted eggs are carried away by adventurers and wandering monsters? 

Mechanically, used some bits of the (AD&D) Froghemoth and the (Dark Sun) Fael and stuck them onto a (B/X et al) Cave Bear. I imagine the solo adventurer as being a 4th level Fighter (YOU are the Hero).

Hope I've done it justice.

Friday, July 16, 2021

The Perils & Pleasures of Tobacco.

Russ Nicholson/ Warlock of Firetop Mountain/ 1982.

Do you need some quick rules for smoking in your fantasy game (those Dwarves look like they're having a great time) and don't already have them? 

Roll 2d6 of different colours. 

First roll is a beneficial effect, second maleficent. Roll doubles and you keep the benefit roll, but suffer a permanent consequence.

Habitual (dedicated?) smokers make a minimum of one roll a day. You can roll every time your character lights up or every time they're in a smoking situation. Casual smokers take the same risk.

Multiple penalties are cumulative over the day; benefits replace each other.

Perfect Pleasure:

  1. Reaction Roll +1 if you offer cigarettes/snuff/tobacco in your next encounter.
  2. Charisma +1 because you look cool.
  3. Wisdom +1 because take a little time to think things through while you smoke.
  4. Intelligence +1 because it helps you to concentrate.
  5. Morale/Loyalty +1 if you share a smoke with your hirelings/followers.
  6. Reroll failed fear save if you light up afterwards.
Vile Custom:
  1. Reroll successful fear save because of withdrawal nerves.
  2. Charisma -1 because it's a low and filthy habit.
  3. Strength -1 because you just went a little bit dizzy there, that's all.
  4. Dexterity -1 because you're fiddling with your smoker's gear, if you're not actually smoking.
  5. Constitution -1 because you just need to catch your breath, that's all.
  6. Reaction Roll -1 because it's intimidating/irritating/disrespectful.

Consequences of your actions:

    11.  -1 of your max. hp now or a full HD off your unrealised potential maximum.
    22.  -1 Dexterity.
    33.  -5 years of life.
    44.  -1 year of life.
    55.  -1 Strength.
    66.  -1 Constitution.

You'll need to work out the length of your character's lifespan and then start counting backwards. Once you hit your current age, you will fail any disease saves and lose d3 from each Ability Score per month until you're helpless and/or dead.

Giving up smoking allows recovery of 1 year/hp/Ability Score per year you don't fall back into the habit, but you never get back your first permanent losses in any categories. Smoking damage might be one of those things (like radiation poisoning) that doesn't respond to magical treatment.

I've made this with humans in mind, but we know that of the basic vanilla fantasy kindred at least Dwarves and Hobbits smoke, too. Either treat them the same, or say that their biology is in greater sympathy with smoking so they get none of the positive or negative effects.

Whether it's actually tobacco they smoke is another question.

My gut says that Elves don't smoke (but might take snuff), and that Ogres go for huge reeking cigars that double as improvised weapons. Wizards won't be told it's bad for them, which is why 'embarrassment of liches' is a collective noun.

There's an entry for Tobacco in the Ghastly Affair Presenter's Manual - gives you the asset of Patience.

Give up smoking. Don't start smoking. Don't scrub it from old movies. Use it for traditional sacred purposes. Fuck tobacco companies throughout history.

Wednesday, July 14, 2021

THE SLEEP PARALYSIS DEMON - Monster for Old School Fantasy & Horror.

It was going to be this or Fuseli's The Nightmare, wasn't it?

Armour Class Unarmoured     Hit Dice ½     Move 50% Normal Human     Morale 6

Neutral (evil) with Unratable Intelligence

An oneiric phobophage, trolling the borders of sleep.

Not every sleep paralysis episode is a demon, and it’s not necessarily a demon.

It can be a man with a hat, a hooded figure, a thing without thumbs, a ghoul, a ghost, a goblin, the incubus-succubus, a recently dead relative, your double, someone else's double, a dolphin transformed into a handsome young man, the Old Hag, a coiled snake, a house cat, a caterpillar, a spider as big as a pony, wings beating against your face and chest, an old woman combing her long shaggy black hair, a dead person on you, a little jewel-eyed idol, an enormous dog or cat, a demon lover, your favourite childhood toy, a side of beef, an astral body, a glistening blood red horse, a statue, a mossy tree trunk, a gargantuan pig, a toad, a tombstone, a single piece of straw, a wheezing voice calling for "more weight", nothing you can see.

It has a thousand forms, appearing across cultures and history.

By day, it barely exists - a thing without shape, sapience or senses. It cannot be detected except by extraordinary means. Second sight glimpses it, but makes no sense of what was seen. The demon wanders without trace or volition.

As night falls, it gravitates towards intelligent beings as they settle down to sleep. Second sight may catch it, mistaking it for a small animal slinking through the shadows - if the demon is surprised, the form that it shows its victim will be seen (save vs. fear as a watcher, below). 

Randomise/pick a PC/NPC as a subject, likewise the hour of the demon's visit. It will come when the subject is alone or asleep or when everyone else is asleep/suitably diverted.

Under ordinary circumstances, only the victim can see, hear and feel the demon, and must make three saves against sleep paralysis per visit.

Three successes or a single crit. Paralysis is broken and the demon vanquished; it will not prey on this character again.

One fail. You have a horrible night. The demon feeds and it as if you have had no rest at all - you are Fatigued as well as any other consequences of losing a night's sleep.

Two fails. Fatigued as above, and the demon will come back again tonight for another go. 

Three fails or a single crit. The demon latches on, visiting you night after night. You make saves vs. charm, disease, fear and illusion at disadvantage, in addition to losing sleep. Thereafter, only a critical success or other means will vanquish the demon - three successes only ensures your Fatigue doesn't get worse.

Fatigue is cumulative: Exhausted, then Spent, and then you make death saves each night to see if you wake up at all. While under the influence of the demon, you are in an Altered State.

Sleeping in a protection from evil circle (or an equivalent effective traditional folk remedy) allows you to get an undisturbed rest and reduce your Fatigue, but does not break any link between you and the demon.

Having someone watch over and wake you from paralysis episodes will prevent your Fatigue worsening - if they're prompt, you won't have to risk any saves.  

The watcher must roll to see if they are surprised by the demon. If they are, they will catch a glimpse of it and must save vs. fear or be frightened - all ability checks and attacks at disadvantage while watching over the sleeper thereafter. On a critical success the demon is vanquished; on a critical fail the demon will visit the watcher next time they sleep, and they will make their saves at disadvantage.

Using detect evil or detect invisible carries the same risk as being surprised.

Other than withdrawing, the demon's only defence is to make a fright attack. As above, but a crit success does not vanquish. It may make one per round.

It is immune to non-magical damage, except where appropriate for an effective folk remedy. A bless spell vanquishes the demon, no save.


Did you ever have sleep paralysis? I have - with the murky dark-on-dark shapes and the pressing feeling and the desperation to make a sound, twitch a limb to break it. 

These mechanics can serve for mundane sleep paralysis and/or SADS, if you don't want them attached to a monster. The spells mentioned probably don't do you any good, in that case.

Unless the demon latches on to you, I think you can probably get away from it by sleeping somewhere else. This could be as easy as changing rooms (its senses are rudimentary, its intelligence negligible) or as significant as leaving the region/country.

And there's not sleeping on your back, too.

There are numerous traditions that the demon has a hat you can grab and pull out of the dreaming. Wouldn't that be a thing to see?

The dreaming may also touch the Astral/Ethereal/Spirit Plane(s), depending on the setting cosmology, so the sleep paralysis demon may have another form or be the minion of something that dwells there.

While it could be a pushover for your traditional fantasy adventurers, it's almost impossible to detect or fight if you're nearer the Normal Human end of the spectrum. It's not meant to be a combat monster, but to make your life miserable until you can find some way of dealing with it other than hoping for good dice rolls. If you're all willing to play the fiction and the mechanics, you can even pretend that there's no monster threat until properly diagnosed.

In another iteration it doesn't have to be a monster in its own right, just some of the abilities of a ghost/haunting - like the Walker Alone.

Owes a debt to the Nightmare from Dragonwarriors Book 4 and the Dreamslayer from Spelljammer (for crits on saves, too).

Thursday, July 8, 2021

THE WALKER ALONE - Monster for Old School Fantasy & Horror.

Don' Look Now/ Nicholas Roeg/ 1973

Armour Class +5     Hit Dice 4+3     Move Normal Human     Morale 11

Neutral (evil) with Unratable Intelligence

It's a ghost. A haunt. It walks where it walks, alone. 

Sort of.

It abides in the places that you'd think there'd to be ghosts, places to which stories accrue. Sometimes it makes those stories, other times it slips in and fits within a pre-existing tradition. Give it an identity and it won't disabuse you of that notion, allowing you to interpret its acts as typical to that personality, that history.

It appears as a young woman, a gargantuan spider, a hoofed shaggy beast, two little girls, a man without skin, a child with no face and its feet on backwards, you, a carpet of creeping things, a dog with a human head, a rat with human hands, a celestial radiance just around the corner, her, something twitching and gobbling behind the curtain, a spinning top whistling at the top of the stairs, the shadow of a bird dying in its cage, him, a boneless thing of plaited hair, a spectral horse, a historical villain, a headless bear rolled thin like pastry, a column of glowing gas, an empty wedding dress, a dear little pig, them, a bulky cigar-smoking shape in an upholstered chair, a hanging judge, long-nailed children with a dark ragged hole in their breasts, a tide of blood, the shifting pareidolia of the fittings and furniture.

It has no personality of its own, but accumulates characteristics from the living and the dead things, the things said and the things written in and about its locus. It does not read minds, but it can know secret thoughts.

In sunlight, it is intangible, invisible, powerless and silent, but may hint its presence in dense fog or smoke, interior gloom, or subterranean spaces. 

Those with the second sight will also catch glimpses, whispers, suggestions of a scent, a breathe of air in passing, raised hairs on the arms and neck, the sense of being stared at.

If you are surprised, then you see slightly more than you want to and must make a fear save or let go of whatever you are holding. On a critical failure, you are frightened and make ability checks and attacks at disadvantage until you have a had a good night's sleep.

When a new person arrives at the Walker's locus, make a Reaction Roll to see if it takes a particular shine to them.

A Hostile result means they will be the focus of a campaign of terror and torment.

A Friendly result means that they will be the recipient of unsettling gifts and eerie attempts at affection/ sympathy, and there will be outrageous retributions against those who harm, upset or otherwise inconvenience them.

It can have one of each mortal focus at a time, and can sense their presence and general location within d4 miles. It will remember/remain faithful to them for d6+1 months if they leave and no one new replaces them.

During the hours of darkness, the presence becomes more active and more tangible. 

It can become invisible at will and can appear in any form it wishes (see above). It can use any language spoken or written within d4 miles of the locus, including ancient and dead languages.

You are unable to look at it directly as it roams the locus, so you can never be truly sure what you are seeing (use mechanics for avoiding a gaze attack). Because of this, the Walker hides and sneaks with advantage (when it is not invisible). It cannot be targeted directly by spells.

If it surprises you, then you see much more than you bargained for and must make a fear save. Failure means you let go of whatever you were holding and are frightened until you get a good night's sleep.

It is able to use the following spell-like abilities, each with a cooldown of d4 hours each:

  • continual darkness.
  • hallucinatory terrain: more robust than the named spell and not cancelled by touch; INT checks to disbelieve, CHA checks to convince others; as well as the usual applications, can be used to make doors, windows and other exits vanish or seem barricaded, or overlay what is already there so you miss your footing.
  • hold person: can be applied RAW, but can also be used to contain those affected at the locus for the rest of the night, a subdivision of this for d3 hours, or specific sub-location for d6 ten minute turns. Or use spell duration.
  • phantasmal force.
  • web (ectoplasm, if you like).

It can use audible glamour, and ventriloquism at will. 

If not otherwise dispelled, all these effects end at daybreak.

The Walker can cause d6 non-lethal damage, striking vs. unarmoured, per attack (STR or DEX check not to be stunned, knocked down or pushed). It can also suffocate/strangle to unconsciousness, but not to death - save vs. spells/paralysis to resist/break free.

If not before, then lost hit points and/or ability scores are recovered at daybreak.

You can treat it as an Invulnerable Monster for purposes of trying to fight it but its ability is immunity is non-magical damage, rather than magic weapon to hit, so you could treat this damage as non-lethal - good only for driving off its immediate manifestation or giving you the false feeling that you're achieving something by violence.

Even magical damage will only drive it away for a time (d6+1 months).

Something exists within d4 miles of the central locus that when confronted with, the Walker will instantly vanish forever. Most likely would be associated mortal remains, but it could be a hard truth or historical fact, buried treasures or legal documents.


Vancian magic and regenerating Trolls were something I could easily get on board with when starting out with D&D, even if they did not reflect the fiction I was expecting.

But Ghosts, I think, were my first big disappointment. 

Firstly, they were not in the Basic set. Second, the stats I saw for AD&D were clearly a monster challenge.

They did not really reflect the ghosts (fiction and non-fiction) I'd already been exposed to and their place on the undead threat scale meant they weren't going to feature as much as I'd want.

It felt like a flaw in the system.

BECMI still had the power scale problem, but the Companion set Haunts, Phantoms and Spirits made for interesting reading/thinking.

The Ghost as presented in Call of Cthulhu and Dragonwarriors (and then the Barudath in Book 4) were much more what I was looking for. So I had those to work with.

Things like the Ravenloft setting introduced more options for shaking up the standard undead (Van Richten's Guides).

The Walker Alone, though, is actually mostly a Wight, as detailed in Dragon magazine 180. The 27th part of The Voyage of the Princess Ark gives details of what happens when you die (other than rolling a new character, undeath or being raised).

When a Wight kills you, it then goes into a nightly trance to hunt your soul and devour it on the plane of Limbo - and it's got special powers! That's the mechanical basis for the Walker, with a little bit of the Fiend Folio Astral Searcher, and a lot of ghost traditions (experience, folklore, fiction, spiritualism and parapsychology).

The Walker Alone (and all ghosts) is not necessarily a spirit of the dead, but it may act like it is and you may believe it is. It is a haunting, in the same way as the Drummer of Tedworth or the Amityville Horror or Hill House and the Overlook Hotel and will seem to respond as such. Until it doesn't.

If you 'invite it in' (and this is deliberately ambiguous), it is able to cause physical harm: 2d3 lethal damage claw attack + fright attack as if it had surprised you. Claw damage blocked by armour, but not the fright attack. Maybe inviting it in also allows possession.

I've left lots of gaps, because the milieu this draws on is more M.R. James than Robert E. Howard. For heroic direct action, I think we're looking at things like oil of etherealness, truesight and fighting it on the Astral Plane - in which case, why not make it a RAW Ghost when you get there?