Simplifying Magic Resistance for B/X

In furtherance of my new d30 project mentioned in recent posts, I'm working on a demons encounter table. As a fan of Tom Moldvay's approach to creating a clear hierarchy for monsters with different strengths (a la Basic's dragons and many of his creatures in Lords of Creation), I'm attempting something similar as I adapt (and expand) the demons from the various AD&D resources. 

Something B/X doesn't really accommodate in its RAW, but I'm also not willing to fully abandon, is the concept of Magic Resistance as a stat for demons (even at very low levels/Hit Dice). 

Eric Diaz over at the Methods & Madness blog wrote about this a couple of years ago. I agree with Eric that only a few creature types should have this kind of magic resistance, and I do generally like the suggestions he's made for handling this. That being said, neither quite fits my personal style or house rules approach, so here's what I've come up with...

Magic Resistance

Some creatures (most notably demons and other supernatural entities) possess an innate Magic Resistance that disrupts spellcasting around them. When a spell is cast upon such a creature, there is a chance the magic simply fails in its presence.

Essentially, Magic Resistance (MR) permits a “preemptive” Saving Throw for a creature with this trait against magical effects. If the MR check succeeds, the creature ignores completely the spell or effect; if the check fails, the creature is affected normally by the spell or effect.

To resolve Magic Resistance, start with a base target of 10, add the caster’s level, and then subtract the creature’s Magic Resistance rating (typically 1–20) to determine the final number needed on a d20 roll (made by the DM for the creature). If the roll result meets or exceeds this number, the spell or effect fails against the creature, otherwise, the spell or effect affects the creature normally. A spell or effect with a target chance of 1 or less will always fail against the creature and a spell with a target chance or 20 or higher will always succeed.

• Cast Against/Direct Interaction: MR functions against targeted spells (e.g., charm person, magic missile) and, if successful, negates the spell entirely.
• Area Effect: If MR succeeds against an area effect, the resistant creature inside the area can ignore the effect entirely, though it affects others around them normally unless they are also magic resistant.
• Proximity: MR does not affect any spell simply because it is cast nearby; the spell must target or affect the creature directly.
• Environmental Magic: MR is not effective against indirect magical consequences (e.g., Earthquake causing a ceiling to fall, or a magical charm causing a rock to fall), only the direct energy of the spell.
• Duration: The resistance is innate, always active, and even applies to beneficial spells (e.g,. even a cure light wounds spell cast against a magic-resistant creature would require a check to see if the spell succeeds, regardless of the wishes of the magic-resistant creature).
• Ongoing Effects: For spells or effects that persist or repeat (e.g., cloudkill, wall of fire), Magic Resistance is checked once per round of exposure; a successful check negates the effect for that round only.
• Magic Items: Magic Resistance also applies to spells or spell-like effects produced by magic items (e.g., wands, rods, staves, scrolls). Instead of using caster level, the DM should apply a flat adjustment based on the item’s strength: weak items (e.g., most wands) are treated as +5, intermediate items (e.g., most rods) as +10, and strong items (e.g., staves) as +15.
• Standard Saving Throws: Even if a Magic Resistance roll fails, the resistant creature is still permitted any standard Saving Throw to avoid or adjust consequences of a spell or effect as prescribed by that particular spell or effect (e.g., if a Magic Resistance roll fails against a hold monster spell, the resistant creature is sill permitted the standard save vs. spells to avoid the effect).

Reaction Tables for Creatures with Low Intelligence

If you've seen my article in the Petty Gods Expanded Edition, have a copy of Fang, Faith, and Legerdemain, you know that I don't feel like a single reaction table is broad enough to cover every D&D encounter. While the Hippocratic Humorism approach of those tables works okay for intelligent creatures, I realized it wasn't really good for non-intelligent creatures or those with only animal intelligence. Those are creatures that react based mainly on instinct. 

As part of a yet-to-be-announced d30 project I've had in the works quietly for the last couple of years (and hope to be able to tease more substantially this summer), I've worked out the following Reaction tables based on instinctual behaviors. 

More to come!

French-Inspired Campaign

I haven't told my players group yet, and we haven't gamed regularly in quite some time, but I'm hoping to pick back up this summer with a bi-weekly session. (Fingers crossed the summer allows it after I return from a delayed honeymoon). 

I'm working on some encounter areas and a map based on a personal version of Clark Ashton Smith's Averoigne stories. But I'm also planning on supplementing with a whole host of creatures out of more traditional French legend/mythology. 

Below is the working version of the list, and my goal is to stat a few a week from now through early June. I may be dropping some of those here as I go. Even if I don't do much with the campaign setting, at a minimum, I'll likely collect the monsters into a published book in the 6"×9" format like the Creature Cache (available in print from Lulu.com and in PDF from DriveThruRPG). 

Working List: "Bestiaire Fantastique" (a.k.a. "Le Grand Grimoire")

1. Ankou (medium undead)
2. Babau  (large dragon)
3. Barbegazi (small humanoid)
4. Bigorne (medium monstrosity)
5. Camba Crusa (small aberration)
6. Carcolh (huge monstrosity)
7. Cheval Gauvin (large fiend)
8. Cheval Mallet (large fiend)
9. Chevalier Géant (huge giant)
10. Chicheface (medium monstrosity)
11. Chien Noir (medium fiend)
12. Codrille (large-to-gargantuan dragon)
13. Coulobre (huge dragon)
14. Craqueuhhe (medium undead)
15. Dame Blanche (medium undead)
16. Dame Verte (medium undead)
17. Dard (large dragon)
18. Dormette (tiny fey)
19. Drac (large dragon/shapeshifter)
20. Duphon (small monstrosity)
21. Ech Goblin (small humanoid/shapechanger)
22. Fadet (small fey)
23. Fion (small humanoid)
24. Gargouille (huge monstrosity)
25. Gavant (medium monstrosity)
26. Giant, Basajaun (large giant)
27. Giant, Jentil (huge giant)
28. Giant, Mairu (large giant)
29. Giant, Tartalo (huge giant)
30. Goubelin (small fiend)
31. Groac'h (medium fey)
32. Guivre (huge dragon)
33. Houeron (medium fey)
34. Houle (medium fey)
35. Irrwurz (small plant)
36. Jetin (tiny humanoid)
37. Karnobo (medium fiend)
38. Loup Garou (medium humanoid/shapechanger)
39. Lupeux (medium fiend)
40. Marioche (large fiend/shapechanger)
41. Matagot (small fey)
42. Melusine (medium fey)
43. Nain Rouge (small humanoid)
44. Peluda (huge monstrosity)
45. Peteu (huge monstrosity)
46. Picolaton (medium monstrosity)
47. Quinotaur (large monstrosity)
48. Rô (huge dragon) 
49. Tarasque (gargantuan monstrosity)
50. Tempêtte (medium fey)
51. Varou (medium undead/shapechanger)
52. Volo Biou (large monstrosity)
53. Vouivre (huge dragon)
54. Yan-gant-y-tan (medium fiend)

Silvered Weapons Information

One of my long-term projects is to continue collecting and expanding my house rules into a sort of "BX DMG."  A lot of these were compiled into RS1 Fang, Faith, and Legerdemain (like the manufacture of holy water, arming and disarming traps, and alchemy rules), But there are a lot of cool things I have planned for this future edition (like information for creating campaign-specific pantheons to support thing like this worksheet).

Today's information comes via my home campaign, where they players were a good distance from civilization and found themselves facing a den of werewolves. They realized that they were significantly short on silver ammo and tried to improvise. With a bit of hindsight, it turns out that what I allowed them to accomplish in the field was far from reasonable, even in the context of a game. 

So, to that point, below are my revised house rules for silvered weapons.

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SILVERED WEAPONS

In many campaigns, there are creatures may only be harmed by silvered weapons. Although it is ultimately up to the DM to determine which creatures are affected by silvered weapons, these typically include: lycanthropes and other shapechangers, certain demons & devils, a number of undead, and a selection of fey and spirits.

A silvered weapon is one whose striking surfaces have been plated, bonded, or inlaid with sufficient silver to count as “silver” for purposes of overcoming specific creature defenses. 
Silvering a weapon does not make it magical. It merely allows the weapon to strike creatures vulnerable to silver. 

PROFESSIONAL SILVERING

Silvering Normal (Mundane) Weapons
Any normal, non-magical weapon may be silvered, assuming there is access to a properly equipped forge and a qualified smith (a master weaponsmith, silversmith, or white-smith). In small settlements, such equipment and/or expertise may not be available.

Standard professional silvering methods include:

• silver plating or bonding onto the striking edge
• silver inlay along cutting surfaces
• partial surface alloying
• reinforced edge wrapping

The time and cost required to silver a weapons is based on the weapon’s maximum damage. 

The base cost in silver pieces equals 100 sp (10 gp) × the weapon’s maximum damage. For example, a weapon that deals 1d4 damage (maximum 4) costs 400 sp (40 gp) to silver, while a weapon that deals 1d8 damage (maximum 8) costs 800 sp (80 gp). This cost includes both material and skilled labor. The silver used represents enough precious metal to properly plate or bond the striking surfaces. 

The time required to silver a weapon equals one day per 2 points of maximum damage (rounded up). Work cannot be rushed without risk of failure. Particularly large or complex weapons may require additional time (at the DM’s discretion).

Pre-Silvered Weapons

In larger towns and cities, merchants may occasionally offer weapons that have already been silvered. These are typically produced in small batches for resale rather than commissioned individually.
Pre-silvered weapons are sold at approximately 75% of the normal custom silvering cost. This reduced price reflects simpler workmanship, thinner bonding, or less refined finishing compared to bespoke work ordered from a master smith.

In regions plagued by creatures vulnerable to silver, demand for silvered weapons increases sharply. Prices for both stock and bespoke silvered arms may rise accordingly — sometimes well above the standard rates (2–3× or more) — or, in heavily fortified settlements, modestly decrease if production is common and competition among smiths is strong. Availability should reflect local fear, trade routes, and access to silver.

While fully functional against creatures vulnerable to silver, such weapons may be somewhat less durable than custom-silvered arms at the DM’s discretion (see Limitations of Silvered Weapons, below). Availability is never guaranteed and should depend upon settlement size, trade activity, and local demand.

Silvering Magical Weapons

As a rule, magical weapons resist alteration. The enchantment binds the material in a fixed mystical state. Attempts to silver a magical weapon generally fail unless special research, ritual, or rare alchemical silver is employed.

The DM may allow such work in exceptional cases, but the work should require significant cost (5,000–10,000 gp or more), substantial downtime (1–2 months at a minimum), and a high risk of permanently damaging or diminishing the weapon’s enchantment (50% or greater).

IMPROVISED SILVERING BY PLAYER CHARACTERS

Characters without access to a silvering resource may attempt to silver weapons themselves. Such efforts are not likely to succeed without the proper equipment and expertise.

To work with silver, it must be brought to full melting temperature. A campfire alone is insufficient unless carefully enclosed and fed with sustained airflow. At a minimum, a small clay furnace, charcoal fuel, and improvised bellows (or steady forced air) would be required for silver to reach workable heat; this might make melting silver to a workable state in the field possible, but far from guaranteed. 

At most, and only with the required heat and equipment, the DM may permit the casting of rudimentary silver slings bullets and the forming of silver arrowheads in the field. Additionally, unless the character (or characters) working the silver have any significant expertise, the resulting silver ammunition is incur minor to major penalties to both “to hit” and damage rolls (–1 to –3) due to flaws in the workmanship. 

LIMITATIONS OF SILVERED WEAPONS

Silvered weapons require occasional maintenance to remain effective.

Silver is softer than steel. Even when properly bonded, a silvered weapon is less durable than an untreated steel weapon. Whenever a silvered weapon rolls a natural 1, it takes a significant amount of damage. After 3 such instances, the weapon no longer counts as silvered. It must then be re-silvered to restore its status as silvered.

Even in the absence of such critical fails, any silvered weapon that has seen significant use during a full adventure is considered to have incurred the same amount of damage as a single failed “to hit” roll with that weapon.

Silver ammunition has lower recovery rate than standard ammunition. Assuming the standard recovery rate for ammunition (non-magical sling bullets and arrows) is 50%, the recovery rate for silver ammunition in good enough condition to be used again is 25%. If not recoverable for re-use, there is 50% chance of recovering the raw silver from the lost ammunition (usually 1–2 sp for a silver arrowhead and 4–5 sp for a silver sling bullet 1 sp for a silver arrowhead and 2 sp for a silver sling bullet).