THE CASEUS CODEX (OSR variant Magic System)

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Klibbix!

Depraved Necromancer
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If I haven't mentioned it before, I love Necromancy in fiction and gaming. There's just something about the darker side of magic that gets to me. I also love systems that tinker around with Vancian magic, and while I love that as well, I am particularly interested in rules that highlight the corrupting effects of magic. The OSR Banterings thread has also reaffirmed my love for games that mutate existing rules into new forms and the ease at which they can be incorporated into a tables game of choice.

Hence my attempt in this thread to modify magic into one of my preferred genres of play, dark fantasy. I'm trying to make it as system-neutral as possible with the baked-in assumption that there are no Clerics or Magic Users and anyone can use magic, or Work as it is called here, as long as they know it. My preferred game would be classless, with everyone effectively a Fighter and starting with one Work. I may eventually try to create a custom class, but that's down the road.

THE CASEUS CODEX


Using Magic

When you attempt Magic, here called a Work, you roll a pair of six-sided dice, called White Dice, and add your Intelligence Modifier. Alongside these White Dice are rolled as many Black Dice as the caster wishes, with a minimum of one for each roll. Black Dice are a measure of Magic's corrupting influence and also allow a practitioner to 'push their luck' to achieve higher results on the respective Work Results Table. A Necromancer, if they so choose, may add the sum of any Black Dice rolled to the total of their White Dice and Modifier, but must take the sum of the Black Dice in points of Corruption.

To determine the results of a Necromancer's magic, consult the table below. If at least one Black Die comes up as a one, the lowest result on the table is triggered and the player chooses which White Die is the amount of Corruption gained and which is the result on the Eldritch Catastrophe Table of the respective Work.
Codex1.png


Corruption

Corruption is the measure of the degradation of a Necromancer's body and soul brought about by their use of magic. At character creation, Necromancers add their Constitution and Wisdom attributes together and divide that total by two, rounding up. They then add their level to this score to determine their Capacity. Each time they attempt a Work, they have a chance to accumulate Corruption. If their total Current Corruption ever equals their Capacity, they roll on the Corruption Effects Table to determine their fate and then reduce their Current Corruption to zero. Any additional Corruption over their Capacity is marked down as Permanent Corruption. Necromancers remove 1d6+half their level in Current Corruption points each time they rest.

Corruption Effects Table
To be finalized at a later date, but the notes below are what I'm aiming for.
1: You transform into a Ghoul. You cannot abide the daylight and suffer -2 to all rolls while in it. In addition, you charisma is permanently reduced to 3 and you can only heal by consuming dead humanoid flesh.
2: An Astral Parasite has attached itself to you. Your Black Dice now trigger on a 1 or 2 until it is removed.
3: You gain an unpleasant feature, such as a foul odor, scaly skin or other such ailments, your Charisma is reduced by two points.
4: You are weakened by your exposure to eldritch energies. Your Strength is reduced by two points.
5: You gain a permanent wracking cough and your Constitution is reduced by two points.
6: Your mind is inundated with Astral vapors and your Wisdom is reduced by two points.
etc, etc.

WORKS
Following are some examples of the feel I'm envisioning.

Animation
Ye Beckoning of Ye Restless Dead
The Whispered Word of Akla-Alkar
The Seventeenth Page of Abbot Bethlam's Scrap-book


Requirements
At least 1HD of CORPSE.

Casting Time
10 Minutes

Effect
Raise up a 1HD Servitor. Servitors are mindless, shambling corpses or skeletons. They move at 60' (20'), have an Armor Class of 11 (8), add +1 to hit per HD and deal 1d6 damage. They may only obey the simplest of commands but will perform them tirelessly and without question. Servitors last until destroyed or until their their creator wills their demise.


Animation Dark Benediction Table
6: Raise up as many 1HD Servitors as you have levels, provided enough HD are available
5: Your Servitors deal 1d8 damage, instead of 1d6.
4: Your Servitors have +1HD.
3: Your Servitors have Max HP.
2: Your Servitors have an additional +1 to hit.
1: Your Servitors move at 120' (60')

Animation Eldritch Catastrophe Table
6: You suffer an additional 1d6 points of Corruption.
5: The corpse rises up as a 1HD Servitor and attacks you and your companions.
4: The corpse rises up as a 1HD Servitor and attacks you and your companions.
3: The corpse rises up in a swarm of 1d3+1 1HD parts (hands, head etc), and attacks you and your companions.
2: The corpse rises up with HD equal to your level +1 and attacks you and your companions.
1: All corpses within 100' rise up as 1HD Servitors and attempt to consume you, and you alone.

Eye of Caustic Sight
Ye Devilish Glance
The Seventh Page of Abbot Bethlam's Scrap-Book
Gaze of the Black Sphinx


Requirements
An eye from a CORPSE.

Casting Time
Instantaneous

Effect
Your gaze becomes blistering and causes flesh to steam, bubble and slough off the bone. A single target within 30' takes 1d6 damage for every level you possess and may Save for half-damage.

Eye of Caustic Sight Dark Benediction Table
6: Your gaze affects an additional 1d3 targets.
5: Your gaze can affect any target within 100' as long as you know they are there.
4: Your gaze can detect Invisible or Astral targets and affect them.
3: Your gaze permanently destroys a piece of mundane equipment the target possess.
2: Your gaze stuns an affected target for 1d3 rounds.
1: Your gaze can dispel any one protective Work the target has currently active.

Eye of Caustic Sight Eldritch Catastrophe Table
6: You suffer an additional 1d6 points of Corruption.
5: You are Blinded for 1d6 x 10 minutes.
4: Your gaze affects a random companion or ally for half-damage.
3: Your gaze affects 1d3 random companions or allies for half-damage.
2: Your gaze is reflected inwards, take half-damage.
1: Your gaze is reflected inwards, take full damage.

Fearsome Steed

Requirements
At least 1HD of horse or other beast of burden CORPSE.

Casting Time
10 Minutes

Effect
You summon, from beyond the stars, a Fearsome Steed to carry you aloft. The Steed looks like the worst combination of locust, lion and leech. It will carry you to any place on the material plane you have been to before and then vanish. Regardless of distance, the journey takes half an hour.

Fearsome Steed Dark Benediction Table
6: Your Fearsome Steed will carry an additional 1d3 riders.
5: Your Fearsome Steed will carry an additional 1d6 riders.
4: Your Fearsome Steed remains and will obey you for 1d3 additional trips.
3: Your Fearsome Steed remains and will obey you for 1d6 additional trips.
2: Your Fearsome Steed will carry you anywhere on the Mundane Plane, even if you have not been there before.
1: Your Fearsome Steed will carry you anywhere, including different planes of existence, even if you have not been there before.

Fearsome Steed Eldritch Catastrophe Table
6: You suffer an additional 1d6 points of Corruption.
5: You suffer an additional 1d6 points of Corruption.
4: Your Fearsome Steed strands you on a barren, lifeless world for 1d6 hours days before returning and carrying you home.
3: Your Fearsome Steed strands you on a barren, lifeless world for 1d3 days before returning and carrying you home.
2: Your Fearsome Steed strands you on a barren, lifeless world for 1d6 days before returning and carrying you home.
1: Your Fearsome Steed attacks you and, if it kills you, carries your body away into the void forever.
 
I like the atmosphere evoked and also the gaining of corruption mechanism.

I wonder about the numbers though: if I have understood correctly on any casting at least one black dice must be used with therefore a minimum 1/6 chance of an Eldritch Catastrophe then occurring.

Several of the catastrophes look pretty bad news.

A PC caster will presumably cast a given spell many times during play and so the odds are that one of the bad news catastrophes will occur sooner or later.

Perhaps some way of mitigating such catastrophes by say extra rituals and incantations (additional time and may-haps expensive components) would be helpful?

Or is it intended that casting is only used in extremis - in which case what does the caster do when not casting?
 
Thank you for the feedback!

Indeed, the numbers are where I'm the weakest.

I wonder if making the Black Die a d8 would mitigate that somewhat. With a D6 you have a 16.67% chance of getting a 1 and with a D8 it's 12.50%, so it could make it a little rarer. I had envisioned that magic itself would be much rarer, given the consequences, but a system that's too punishing might make any PC hesitant to actually use it, which obviously defeats the purpose.

I do like the idea of the extra ritual and incantations helping out as well, perhaps for bonuses on the table itself. As it stands, I wanted to ensure that practitioners have to balance Corruption gained vs. extra options on the Dark Benediction Tables, but I'm sure there's another way to enforce that.
 
Invocation of Hag-Thalak

Requirements
100c in various materials, at least 1HD of CORPSE, Spell must be cast at Midnight.

Casting Time
1 Hour

Effect
Your chanting reaches the depths of the Astral Plane and awakens Hag-Thalak, the toad god. He appears astrally nearby, pleased by your offerings, and will grant you one option from the spells Dark Benediction Table.

Invocation of Hag-Thalak Dark Benediction Table
6: Summon Child of Hag-Thalak: A Child of Hag-Thalak materializes nearby and will obey your commands for 1d3 days.
5: Finder of Lost Things: The Toad God whispers the location of any object to you, no matter where it is.
4: Blessing of Hag-Thalak: The touch of the Toad God will cure 1d3 targets you choose of any disease, mundane or magical.
3: Form of the Toad God: For 24 hours you may transform yourself into a common toad, and back again, as many times as you wish.
2: Sigil of Hag-Thalak: The Toad God places his sigil on any nearby portal. It will deal 1d6 for every level you possess to any who open it. This lasts a week or until you dismiss it.
1: Breath of the Toad God: If you command, Hag-Thalak will turn your level x 10' of stone into stinking mud.

Invocation of Hag-Thalak Eldritch Catastrophe Table
6: You gain an additional 1d6 Corruption.
5: Hag-Thalak invests you with a plague of painful boils. You suffer -2 Charisma and -2 to all actions for 1d3 days.
4: The Toad God vindictively hides one of your treasured items, preferably magical, in a cyst deep beneath the earth.
3: Hag-Thalak transforms you into a toad for 1d6 days.
2: Hag-Thalak inflicts you with a wasting disease. You lose 1 permanent HP each day until cured by magical means.
1: The Toad God sends one of his Children to attack you, the Child will materialize in 1d3 days.
 
Thank you for the feedback!

Indeed, the numbers are where I'm the weakest.

I wonder if making the Black Die a d8 would mitigate that somewhat. With a D6 you have a 16.67% chance of getting a 1 and with a D8 it's 12.50%, so it could make it a little rarer. I had envisioned that magic itself would be much rarer, given the consequences, but a system that's too punishing might make any PC hesitant to actually use it, which obviously defeats the purpose.

I do like the idea of the extra ritual and incantations helping out as well, perhaps for bonuses on the table itself. As it stands, I wanted to ensure that practitioners have to balance Corruption gained vs. extra options on the Dark Benediction Tables, but I'm sure there's another way to enforce that.
It is punishing but think that is the intent. Another die type can help quantitatively but qualitatively it will likely feel the same, even if you went to a d10 or d12.

Another approach is perhaps you can lower your roll by x points to remove 1 back die that reads 1. I'd also remove the spell failing on a black die that read 1...it works but with the corruption etc.

Give the player a choice as sometimes the situation may demand they keep the black die that read 1, so the spell takes effect.
 
Succeeding with a 1 is a great idea. What I really want to do is push choice, as you mention, and also push Corruption. So instead of any failure whatsoever, with your idea, we would only have 'critical' success, regular success and success with Corruption/Eldritch catastrophe. Makes it more interesting as well, something always happens.
 
Alright, I've tinkered around with the Table results. Here is the newest version of how Magic works. I've tried to incorporate the feedback I've received. In this version, when a Black Die comes up as 1, there is a choice to instead succeed and avoid the Eldritch Catastrophe Table but the Necromancer takes permanent Corruption as a result

USING MAGIC

When you attempt Magic, here called a Work, you roll a pair of six-sided dice, called White Dice, and add your Attribute Modifier. This modifier can be from any attribute the GM desires, or even a separate one of their own devising. Alongside these White Dice are rolled as many Black Dice as the caster wishes, with a minimum of one for each roll. Black Dice are a measure of Magic's corrupting influence and also allow a practitioner to 'push their luck' to achieve higher results on the respective Work Results Table. A Necromancer, if they so choose, may add the sum of any Black Dice rolled to the total of their White Dice and Modifier, but must take the sum of the Black Dice in points of Corruption.

To determine the results of a Necromancer's magic, consult the table below. If at least one Black Die comes up as a one, the lowest result on the table is triggered and the player must choose: take the highest White Die in points of Permanent Corruption and move their original result two steps up the table, or take the lowest White Die as as the result on the respective Work's Eldritch Catastrophe Table.

Newest Corruption.png
 
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