Using this example rune above, here is a walkthrough of using this rune magic system. I start with the core mechanic first, and then provide optional rules to increase character success, enhance player choice, create meanginful spell preparation, and simulate the ebb and flow of magical energy.
Runes are found magic objects with a magical inscription that provides spells to a wizard. Those that can unlock the secrets of the rune can use it to cast spells specific to the rune.
When a character finds a rune, they make a check or cast Read Magic to unlock the first spell. Checks could be roll under, but not equal to the Intelligence stat or a Learn Spell check from the Intelligence table. In Swords & Wizardry, this would be a Chance to Learn New Spell roll. If the character unlocks the first spell, the referee will provide the details of the first spell including name, spell level, and effect. The referee will also provide the true name of the rune.
The name of the rune provides a theme of the spells the rune contains. In the example above, the true name is Akeeli which I've translated in English as oxidation. The referee decides that this implies that the rune has spells that center around fire or rust. The first spell is Light, but this version has to be cast on an object to provide light.
Casting a Spell
To cast a spell, name the spell and roll 2d6. Check the result against the column with the spell level of the named spell. If the result is empty, the spell is successful. If it is filled, it fails. The wizard doesn't lose a spell level upon a failed rolled.
Yes, that's the basic system. I have a spreadsheet in LibreOffice that allows me to make all kinds of runes from any word I want. I generate a rune, add a number of spells to that rune and make a printout. The referee's version has the entire list of spells possible for the rune, the player gets a blank one with the rune, the name of the first spell, and a description of that spell on the back.
Optional Rule 0 - Spell Selection
At first glance, it may appear that the chances of successfully casting a spell are too low. The most difficult spell to cast with this rune would be a 2nd level spell. The chance of success is 75%.
Still, if other spellcasters prepare spells that just work, there has to be some sort of tradeoff to be a rune wizard. One option is to select spells that a Magic-User would not be able to access, like Cleric or Druid spells. You could add a Cure Light Wounds spell that feels like burning at the site of an injury, but heals 1d6+1 hit points. A typical Magic-User wouldn't have this spell. Maybe the party might be able to use the Cleric for something other than a hospital.
Another option is to make a spell one spell level lower. A Fireball spell at lower levels would be prized by any wizard. Detect Magic as a second level spell would make sense for a rune wizard as they attune to the very language of magic itself. Any third level spell could also fit the theme if the wizard has to use a material component like a candle flame or the tongue of a rust monster. You may even add Clairvoyance but require that the wizard stare at a rusted shield or campfire. These are all 3rd level spells in S&W that might be worth the risk of failure in order to gain access to these spells sooner.
Notice that there is no rule that a rune must have nine spells, one for each level. Runes can be made to have any number of spells. Runes do not require spells for any given spell level.
Optional Rule 1 - Mnemonics
Another option is to have magic items that allow automatically successful rolls. A Mnemonic could be specific to a spell or to a roll. For example, the character may discover or create a Mnemoic that allows automatic success for casting the Light spell. The fiction could be that a tiny diamond on the sleeve of the wizards robe helps them to focus clearly on casting the light spell.
Another form of Mnemonic would be specific to a roll. In ancient languages, numbers tended to be letters (as in Hebrew and Greek), so it would make sense for a rune wizard to attune to a specific letter. In game terms, this means that a Mneomic would make all rolls of a specific result automatically successful. For our example rune, the wizard develops a Mnemonic that makes all rolls of 6 successful. These mnemonics would work for all spells and would not be rune specific.
A third form of Mnemonic would be specific to a spell level. This could be as simple as ruling that once rune wizards reach 8th level that 1st level spells are automatically successful. It could also be a magic item like a wand or staff that allow any given spells at a certain level to be successful.
Optional Rule 2 - Attunement and Frustration
In the example rune, you may have noticed that the rune itself exists between the results of 2 and 6. That was on purpose as I use this option when running the system.
This option classifes runes into three categories, Low, High, and Major. High Runes have an insciprtion at the top of the chart (values 1 to 6). Low Runes have an inscription at the bottom of the chart (8 to 13). Major Runes have an inscription on both parts.
At the beginning of the day, a wizard can choose to atune to one or more runes. This will allow the wizard to roll 3d6 and take the best two to successfuly cast a spell. Using our example rune, this increases the chance of casting a 2nd level spell increases from 75% to 87.5%. A wizard cannot atune to the same rune two days in a row.
The cost for this is that for every rune attuned, there is one that must be frustrated. Using a frustrated rune will require to wizard to roll 3d6 and take the lowest 2. If the wizard foolishly chose to frustrate our example rune, a 2nd level spell would only be successfuly 61.1% of the time.
However, if the wizard chooses to frustrate a low rune, one where the black marks appear in the results 8 to 13, it would actually provide a bonus to use that low rune. As the wizard collects more runes, they will be able to provide bonuses on many, if not all of their runes. The same rule applies to frustration: a wizard cannot frustrate the same rune two days in a row.
Major runes provide a slight improvement whether they are attuned or frustrated. I orginally created these to have rare and/or very powerful spells. A wish would be on a major rune because I don't want wish to be cast successfully very often.
Optional Rule 3 - Tides of Magic
This optional rule explains why there is a 1 and 13 result on the chart. To simulate the ebb and flow of magic power in an area, have the player roll 2d6. If the result is 9 to 13, add 1 to all spell casting rolls. If the result is 2 to 5, subtract 1 to all spell casting rolls. To make magic more wibbly-wobbly, you can say that even results add 1 to the spell casting rolls while odd rolls subtract 1 from those rolls.
Putting It All Together
I plan to use all the options for more experienced players, but only the basic rules + mnemonics for newer players. I like this system because despite the potential for several moving parts, it all comes down to a 2d6 roll + adjustments. I also like this system because the way translated English names appear on the runes, a player could potentially decipher new runes or devise runes of their own.
I recommend that you use Ozymandias' Spell Compendium or similar resources to build runes. Ozymandias' list doesn't include Cleric spells, but you may decide that keep runes arcane. Other resources can provide other types of spells. You can also use domain lists to quickly make runes.
Lastly, I want to thank the Dotsies font for inspiring the way I created the runes. I don't use the font in rune creation, but I wouldn't have had the idea for this system without it.