Chart Based Spellcasting

This post uses a chart that is not obviously reduced down to a simple formula. I say that because you have to give it to Delta. He broke down the Turn Undead table causing me rethink this post. Once you realize that the Turn Undead table is basically rolling 5+ on 1d6, it didn't seem worth presenting the original tweak. It felt like redoing the 2d6 spellcasting class presented earlier.

Where's the fun in that?

Still, I have created a Turn Undead based caster before here. It's not a tweak like my previous posts, but it's there for anyone that wants to use it.

To use a table, the challenge was to come up with a table that was not easily reducible to a simple die roll. After quite a few experiments and lots of research, I attempted to use a drop table or the original FASERIP table.

The drop table is not a bad idea, but my lack of art ability makes this a rather unattractive option. The FASERIP table (and the ZeFRS and 4C variations) were interesting, but it introduces column shifts and basically still feels like a percentage roll. Redoing a percentage roll is too much like another previous post.

So I looked for a chart in any game I have that wasn't so obvious. Despite the fact that it requires custom dice, I ended up choosing Paydirt, the American football simulation game. One reason for the choice was the ability to make something visual within my limited artistic abilities. The main reason was that it was different.

Blah, Blah, Blah, we saw the chart as the featured image.

Using a custom chart means, of course, that I am beyond making small tweaks, but introducing a new mechanic that doesn't exist in any S&W or OSR clone I know. I still plan on using the spell table to be a check on this spellcasters' power, but more on that later.

The link to the chart is here: Spellcasting Paydirt The top row represents the level of the attempted spell. The leftmost column represents the possible dice roll results. Roll the dice, look down the first column for the result and then look right for the level of the spell attempted. Green means success, red means failure. If you choose to use them, purple is a major success and black is a major failure.

Paydirt used some truly funky die. The dice for the chart use the custom dice rolled for offensive plays.

The offensive dice are:
Black die: 1-2-2-3-3-3
White die: 0-0-1-2-3-4
White die: 0-1-2-3-4-5

The Black die was the tens digit and the White dice were added together to get the ones digit. Because of the zeroes, the results range from 10 to 39. When you do the math, the results do not make a simple curve, so looking at the chart does not provide likely probabilities at first glance. Only seven of the twenty-nine cells for a 9th level spell are red or black, yet these are the most difficult spells to cast (about a 50-50 chance). First level spells have eight red or black cells, yet they are the easiest to cast (about a 90 percent chance).

The other appeal of these charts, are that there is some ability to make designs without affecting the odds of successful spellcasting. (If there is interest, I'll make a few.) I thought about using these to represent astrological charts. Let's say a simple die roll (1d6 or 1d8 determined by the number of charts made up) determines which chart is available. The charts wouldn't be too different (although that could be fun, too) but interesting enough that a player is not always trying to roll in the 30s.

Like the other two classes in earlier posts, a spellcaster using this chart is still an unreliable spellcaster. Spells are not guaranteed in the same way as the traditional S&W Magic-User. We could have them make magic items that increase their reliability. We could also have them make potions to guarantee the spell is cast. You can certainly mix and match the special abilities of the previous classes, but let's do something a bit different.

Going with the idea that these spellcasters use astrological charts, let's add in a dash of numerology. At every even level, roll the custom dice to add a magic number to add to the character sheet. Results are cumulative. An 18th level spellcaster would have nine magic numbers. When casting a spell, rolling a magic number results in success. No matter what the result says on the chart (good or bad), rolling a magic number is a standard success, not a major one.

Still, the spellcaster may get no benefit from the magic numbers, even at high levels. Instead of adjusting the XP Chart, we'll add another minor ability, a small hex ability.

This hex ability uses the custom chart to determine success. Roll 1d8 to determine which column to use and roll the custom dice to check the result. A character's magic numbers can also be used to determine success.

On a successful roll, chosen targets within a 20 by 20 foot area are struck with a saving throw penalty for three rounds. If the 1d8 result is 1 to 4, the penalty is -1. If the result is 5 or more, the penalty is -2.

Again, not a tweak, but with a new mechanic, an astrologer or numerologist class with some interesting abilities. Even with the hex ability based on the Prayer spell, it is a class that is still weaker than a Cleric and on par with a standard Magic-User. The choice of a standard Magic-User is still a good one as the M-U always successfully casts whatever spell he or she wants. Want something different? Well, not as reliable, but fairly interesting without being overpowering.

As for a type of magic item that can be found, it could be a gem, a stone, or other kind of object inscribed with a magic word. The word provides another magic number for this class to use on a one-time basis. If you have a houserule that allows all M-U to create scrolls, you can use a similar rule for the creation of these magic words. The cost is 1d8 * 100 gp and take 1d8 days to create. A spellcaster can only use one of these items per spell attempt.

A more powerful magic item cover a group of ten rolls. Specifically, these gematric perfections would make rolls 10 to 19, 20 to 29, or 30 to 39 into successes, regardless of what appears on the chart. The cost of these items would be 4500gp and could be used only once. Unlike the lesser magic item, this expensive magic can be stacked.

In the next few posts, I'll talk about the interchangeability of the four classes and new types of magic items that affect all of them. The goal of this series of posts is a modular system to create interesting NPCs or classes. More soon.

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.

Math Post – Odd Bell Curves

I posted the other day about a mechanic inspired by Target20, a system developed by Daniel Collins:

(d20 + d10) + level + modifiers ? 26

This system assumes the use of descending armor class per older editions of D&D when it comes to combat. So, let's take the case of a 6th level fighter attempting to hit a creature with an Armor Class 5. With this system it would be

(d20 + d10) + 6 + 5 ? 26

Or, you have to roll a 15 or better to hit. The chances of that are 57.5 percent.

In 2e, a similar scenario 6th level Fighter has a THAC0 of 15 requiring an 11 or better with a d20 to hit AC 4. The chance of success is 50 percent.

Not too bad really - I don't mind being a little more generous with combat. But how about lower levels? Let's see:

This scenario is a 2nd level fighter attempting to hit AC2, a tough challenge.

(d20 + d10) + 2 + 2 ? 26

In other words, roll a 22 or better, a 22.5 percent chance of success.

The same scenario in 2e means that the 2nd level fighter has a THAC0 of 19 meaning that he needs a 17 or better to hit. Chance of success is 20 percent.

Saving Throws

When doing saving throws, the basic formula is still the same:

(d20 + d10) + level + modifiers ? 26

This time, though, the modifiers are standard based on the type of Saving Throw: +0 for Spells, +1 for Breath Weapon, +2 for Petrification, +3 for Paralysis and +4 for Death. (At least, this works for Fighters and Clerics)

So, a 6th level Fighter needs to make a Saving Throw against a young dragon's Breath Weapon:

(d20 + d10) + 6 + 1 ? 26

In other words, he has to roll a 19 or better. This provides a 37.5 percent chance of success.

A 6th Level fighter making the same save in 2e has to roll a 13 or greater, a 40 percent chance of success.

Saves in my system are more lethal for higher level characters, but only by a slight margin.

Now because the modifiers are different by class, I would simply put the saves on the character sheet so that a player only needs that reference to roll anything.

Rogue Skills

Doing this take a change in how Rogue skills are handled. Instead of using percentages, skills would have a number that looks an awful lot like a skill rank used in 3e. In other words, Climb Walls wouldn't be listed as 80%, but as +15. Since 2e allows you to start with a base and add points where the player wishes, I'd have to recalculate all new starting points. Climb Walls would start at +11, others would start somewhere between 1 and 5. I haven't worked that out yet.

Anyway, if you have a first level thief with an 80% chance of climbing walls vs a 1st level Thief in Andras with a +15 Climb Walls score...

(d20 + d10) + 1 + 15 ? 26

In other words, he/she would have to roll a 10 or better, an 82 percent chance of success.

More Work to be Done

Still more to be done, obviously. Just a weird idea. Yes, it would be easier to stick to Dan's original idea. His is more tidy in some ways and the formulas don't have this weird 26 all over the place.

Yet, the flat curve works for me. It does some funky things at higher levels that I like. Combat is still not automatic at higher levels, neither are Saving Throws. Maybe it will turn out to be a silly idea after all. As always, we'll see.