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Tag: Magic Systems (Page 2 of 2)

Casting Like a Thief

The first spellcaster relied on the Swords & Wizardry saving throw. The second relied on reaction rolls, very loosely based on Chainmail. This post will talk about using percentile dice like a Thief using his or her skills. Although I written about it previously, the last post in the series will use the Turn Undead table to determine success.

A simple way is to set a percentile chance of casting spells is to each spell level. Set an 85% chance to cast a 1st level spell and subtract 10% for each level after that. Yes, this means that there is a base -5% chance to cast a 9th level spell; there will be more on that later. The 85% number comes from the Thieves' chance to Climb Walls at 1st level.

To make things interesting, there will be two modifiers to the roll. One modifier will be based on the spellcaster's level, the other based on Intelligence. For each level of the spellcaster, the chance to cast the spell increases by 5%. For example, a 1st level spellcaster has a +5% chance of success while an 8th level spellcaster has a +40% chance of success. As far as Intelligence, a spellcaster with an INT of 15 or more gains a +3% chance of success. If the INT is 8 or less, the modifier is a -3% to the chance of success.

Again, the purpose of these classes is to provide tweaks, not rewrite spellcasting classes, so the spell table is still the main method of limiting this class' power. This prevents higher level spells from being cast too soon as compared to other classes. A 2nd level spellcaster without a spell table limit would have a 85% chance of success to cast a 2nd level spell. For that matter, the same spellcaster has an almost two-thirds chance to cast a 4th level spell. So, the spell table remains the limiting factor.

Despite rolling percentage dice, this class is only slightly less reliable than a standard Magic-User. As such, I think it would be fair that this class would lose a spell slot on an unsuccesful roll. This makes them even less reliable, though the risk at higher levels is still pretty small. a 7th level spellcaster can automatically cast 1st and 2nd  level spells. There will be a 90% chance to cast a 3rd level spell and an 80% chance to use their lone 4th level spell slot. Those odds are still pretty good.

Like any unreliable spellcaster, there's a good chance that he or she will attempt to find ways to guarantee success. The skill-based spellcaster makes temporary foci to guarantee success. The Chainmail(ish) spellcaster uses amulets to gain an advantage to cast a spell successfully. Neither of these classes, however, risk losing spell slots. If the magic focus or amulet fails, the spellcaster can try again, even if they don't have any more magic aids to boost their chances.

To make them different from the other two classes so far, let's have this class strive to save the spell slot, instead of increasing the chances of success. It's easy to think about increasing success as somehow stablizing the magic required to perform a spell or increasing the raw magical power being manipulated. The spell slots, though, measure capacity.

If you imagine a spell as being a semi-living creature crawling around in a spellcaster's skull, saving the spell slot can be compared to a trap that snatches the spell back in case of failure. A different way to think about it would be like the safety on a firearm. The spell has to successfully turn off the safety to be cast, but if not, no spell is used up. The spell is still in the chamber, ready for another try.

Stability still requires a cost, mechanically and financially. I'll stick with the tried and true 100gp per level of the spell slot to be saved. Mechanically, the cost will be a -5% modifier to spell success. The physical representation of the safety could be something ingested by the spellcaster before casting the spell. I have not read Brandon Sandersons' Mistborn series, but if you are a fan, this could be used as a basis to make Allomancers. Instead of metal, the spellcaster could swallow powdered gems, or just about anything else. For ease of reference, I'll call these ingestible items Mnemonics.

So this class has four tweaks:

  • Base percentile chance to cast a spell based on spell leve, modified by spellcaster level and spellcaster Intelligence.
  • If the roll fails, the spell slot is lost unless...
  • ... the spellcaster creates Mnemonics that are consumed so that the spellcaster keeps the spell slot in case of failure.
  • Mnemonics cost 100gp per spell slot level and lower the chance of success by 5%.

All in all, not too bad. Because of the ingesting, it is easy to think of this class as an alchemist. If you allow a standard Magic-User to create scrolls in your game, you should allow this class to make potions of their spells.

Fireball spells can be like dragon's breath, or the tiny bead of energy escapes the mouth, your preference. Charm spells can show themselves as songs (or not if you really really hate bards). There's all kinds of creative ways to have a spell come from a potion instead of a scroll. How about the Magic Jar spell or even the Prismatic Sphere?

Wrapping up, here is a spellcaster that uses a familiar mechanic (rolling percentage dice like the Thief) with two tweaks, that turns out to be a type of potion-making spellcaster. The spells may be the same, but he or she will play differently from the spellbook toting standard Magic-User.

Next time, the Turn Undead table.

Something like Chainmail Casting

As a player and a referee, my experience has been that for a class to feel different, the mechanics have to be different. Running one (maybe two) games, I appreciate smal changes or tweaks to existing classes to provide a new experience without having to master a new subsystem. In this post, I look at something similar to the venerable Chainmail magic rules. It may be more accurate to say that it is based more on reaction rolls/morale rules. For reference, the first spellcaster in the series (Saving Throw as Magic skill) is available here.

The best summary of the Chainmail rules I have found is here on Jeff Rients' Site. (I don't own DCC, so I can't speak to the DCC part of the post.) Essentially, roll 2d6 modified by spellcaster's level and spell level. If the result is 8 or more, the spell is successfully cast.

Starting with this mechanic, I want to make a small change. Chainmail did not have nine levels of spells and it seems that spell level and spellcaster level were more closely related than D&D. In other words, a 2nd level magic-user could cast 2nd level spells. Even if I am mistaken about it, the mechanic breaks down if I add the spellcaster's level to the dice roll for Swords & Wizardry. Not only that, there are nine spell levels instead of six. So here is my version of Chainmail-ish spell casting for Swords & Wizardry:

  • Roll 2d6 greater than or equal to 7+ Spell Level for success.
  • Half of the Spellcaster's level, rounded down, is added to the roll.

For those that care about numbers, this gives a first level magic-user about a 42% chance to successfully cast a spell. (Roll 2d6 greater than 8 with no adjustment to the roll.)This is close to the odds for the skill-based spellcaster I wrote about. Just like the previous spellcaster, the spell table is used to prevent spellcasters from launching high level spells before the standard magic-user.

Again, should the spell slot be lost for missing the roll? Not for this class. That leaves our 1st level spellcaster more chances to use the only spell slot.

Since the spell table is being used, we're still left with a class that is an unreliable spellcaster and somewhat less than the standard Magic-User class. We could adjust the XP table, but I want to add class features instead.

The skill-based spellcaster is able to make magic items that guaranteed spellcasting success. If I grant that ability here, I've only re-created the same class with a slightly different mechanic. That's too much the same, so let's try something else.

I do want to provide some kind of boost to the chances for casting spells, so let's do it by adding an extra d6 to roll and taking the best two. We'll say that this spellcaster can make astrological charts, leyline maps, or amulets to improve the chances of success. For the sake of convience, I'm going to call them amulets.

This leaves our poor 1st level spellcaster to improve only to a 68% chance, but as he/she advances, it will become much easier to cast lower level spells. A 2nd level spellcaster has an almost 89% chance of success to cast a 1st level spell. A 3rd level spellcaster has about an 81% chance of casting a 2nd level spell.

What this does is allow better chances without providing a static bonus. Even without gaining an extra die, as the spellcaster progresses casting lower level spells becomes much easier. At higher levels, the spellcaster will not need to pay for the ability to cast lower level spell. He or she will instead spend money to cast higher level spells. Specifically, we'll make it similar to last time: the cost of the improvement will cost 100gp per spell level and take the spell level number of days to create.

If a spellcaster spends 400 gp, he or she gets to add an extra die when attempting to cast a 4th level or lower spell. The amulet(or chart or whatever you call it) will only work for one spell regardless of success. In other words, if the spell still fails using an amulet, the amulet is lost.

At this point, we have a standard spellcaster with three tweaks:

  • Roll 2d6 greater than or equal to 7+ Spell Level for success.
  • Half of the Spellcaster's level, rounded down, is added to the roll.
  • Through making amulets, the spellcaster can add an extra die to improve chances of success taking the best two of the three dice as the result.

We're still left with a class with less spellcasting ability than the standard Magic-User class, so what else can be done?

Let's look at the standard Dispel Magic spell in Swords & Wizardry:

Dispel Magic
Spell Level: Druid, 4th Level; Magic-User, 3rd Level
Range: 120 feet
Duration: 10 minutes against an item

Dispel Magic, although not powerful enough to permanently disenchant a magic item (nullifies for 10 minutes), can be used to completely dispel most other spells and enchantments.

The chance of successfully dispelling magic is a percentage based on the ratio of the level of the dispelling caster over the level of original caster (or HD of the monster). Thus, a 6th-level Magic-User attempting to dispel a charm cast by a 12th-level Magic-User has a 50% chance of success (6/12 = .50, or 50%). If the 12th-level Magic-User was dispelling the 6th-level Magic-User's charm, success would be certain (12/6 = 2.00, or 200%).

Let's use this to provide a counterspell ability, but use a different  mechanic to determine success.

Instead of division, I will use subtraction to modify theroll, adjusting the target number by the result. For the examples listed, a 6th level spellcaster attempting to counter a spell cast by a 12th level Magic-User has no chance of success as he or she would have to roll a 13 to succeed. (12 - 6 is 6, add the adjustment to the target number to get 13.) Turned the other way around, the spell caster has an automatic success (the same as the Dispel Magic spell description). To prevent abuse of the power, The cost will be the highest level spell slot available. At higher levels, the spellcaster will likely cast the actual Dispel Magic spell, but unlike the standard Magic-User, he or she can attempt to dispel more than one spell by sacrificing the highest available spell slot available. For lower level spellcasters, this is a bargain, but the chances of success are much lower. Still, this ability is limited by the number of slots available on the spell table.

Looking at the four changes, we have:

  • Roll 2d6 greater than or equal to 7+ Spell Level for success.
  • Half of the Spellcaster's level, rounded down, is added to the roll.
  • Through making amulets, the spellcaster can add an extra die to improve chances of successof spellcasting
  • A counterspell ability that costs the highest level spell slot available.

I imagine this type of spellcaster being a Magic-Eater (similar to a sin-eater). Through a short ritual, these mages have a natural ability to negate magic at a cost of limiting their own ability to wield spells.

Next time, I'll look at a percentage based spellcaster.

Saving Throws as Skills

The best post I have found about this is on the Akratic Wizardry site here.

There is a Whitebox thief somewhere that uses a Saving Throw with modifiers for Thieves' Skills. (My google-fu fails me.) So I thought about using this mechanic for magic, psychics, or some other weilder of mystic forces.

What follows is thinking aloud, so feel free to skip to the end to get to the conclusion.

The trick is to prevent a first level charcter from being overpowered. 1st level Clerics do not have a spell, 1st level M-U gets one spell. With a skill roll, you can say that the 1st level spell caster using a skil roll gets spell slots like everyone else. With that, what happens if the roll fails? Do you lose the slot?

It seems really limiting to say that the spell caster loses the slot on a failure. Assuming no modifications to the roll, a 1st level character has a ST of 15, so that is a 30% chance of success. Adding a +3 to the roll increases the chance of success to 45%. That seems more fair, a 1st level character character has close to a 50-50 chance to lose a spell slot.

As the character progresses, the chance of success caps at 11th level with 95% odds. Not too bad. What about the chances for more difficult spells?

I could say 3 - Spell Level as a standard adjustment for the spellcaster. This would limit the spell caster to having a 50% chance to cast a 9th level spell. If they are capped at 7th level spells like Clerics, it gets better (60%)

So with two tweaks, I can use the standard M-U or Cleric table for spell casting classes that roll for success. The tweaks are:

  1. Roll d20 against ST + 3 - Spell Level for success.
  2. The spell slot is lost only on a successful roll.

That leaves us with a somewhat unreliable spell caster with the same limits on number of successful spells cast. He or she may get more attempts to cast spells, but absolutely no extra spells.

Doesn't seem fair to have the same advancement tables, yet be a diminished spell caster. While I could change advancement, it makes more sense to me to add a minor ability.

If I learned a form of spell casting that is somewhat unreliable, I would want to find a way to up my chances of successfully casting a spell.

Let's say that this spell caster can create a type of temporary spell focus. This spell focus would allow them to cast one spell successfully without a skill roll. Using a tried and true OSR rule, the cost of the focus would be 100gp per spell level. It will take the spell level number of days to create the focus.

For regular spell casters, this usually applies to creating scrolls to allow for extra spells. For these spell casters that use a skill roll, it would only provide guaranteed spells using up the slots they have available. In other words, a 1st level spell caster could create a focus to guarantee they could successfully cast a 1st level spell. This would count against their spell slots as it is not a scroll.


With three tweaks, you can have a skill based spell caster, with the same tables as Clerics or Magic-Users.

  1. Roll d20 against ST + 3 - Spell Level for success.
  2. The spell slot is lost only on a successful roll.
  3. The spell caster can create items that guarantee spell success, but use the spell slots. The cost of this item is 100gp per level of the spell.

Next post, I hope to look at other alternatives for spell casting.

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