Using Magic Power Sources for Custom Spell Systems

I’ve completed most of the articles in my series on magical power sources. Here are the series links:

Magical Power Source Articles

1. power source table
2. Astrology
3. Words of Power
4. Invocation
5. Occult Forces
6. Psychic Powers
7. Spirit Binding

But I feel I need to explain how this is all meant to be used in more detail, since there was some confusion. OD&D does not describe how spells are prepped. It’s just assumed that magic-users somehow select which spells to use on an adventure. Actual casting by default seems to be just quick words and gestures, since there’s no casting time given. The magical power sources are, essentially, ideas for how spells are prepped.

• Do magicians find the time when the stars are right for the spells they want to prep?
• Do they chant words of power, or call upon deities to bestow the power?
• Do they grind up, mix, boil, or burn ingredients to release the arcane properties within?
• Do they meditate to call upon their own inner mystical powers?
• Do they command spirits to provide the power?

GMs can select one or more of these as the prep method for their main spell systems. My preferences are:

• A mix of astrology, words of power, and occult properties for magic-user spells (arcane spell lists.)
• Invocation (prayer) for cleric spells (divine spell lists.)

But suppose you want another spell system, for example to make the magic in a distant land seem exotic? Or suppose you want high-level spells to be a little harder, with more restrictions? Having a list of the power sources is a good place to get ideas. Plus, you have the table to roll for random sources.

Most low-level spell systems can use a 2d6 roll on the table for 15 different systems that mix two power sources. Read each die result separately: my preferred systems listed above would be (2,4) or (4,2) for magic-user spells. If the result is doubles, there is only a single power source, but it is more limiting: a result of (3,3) would match the preparation method for cleric spells, requiring 1 to 5 hours of prayer and worship to refresh 1st level cleric spells.

If you need an ultra-low-level magic system, roll only 1d6 and reduce the strength of the spells involved, perhaps limiting the spells to a certain theme. For magic systems that are a little more powerful, roll 3d6 instead of 2d6. Thus, the system requires a mix of three power sources, or one limiting power source and one ordinary one, or a single extremely limiting power source. These alternate magic systems can be made learnable, so that spell casters can pick up spirit-binding as another spell system and either choose which method to use for spell prep or learn spells uniquely tied to spirit-binding.

High-level spells – those above level 6, when I run the game – can likewise be designed as bonus spell systems for spell casters to learn. For example, there might be some powerful divination spells that require a mix of astrology and meditation. For these spell systems, roll 3d6 or 4d6 to define the power sources. Quadruple results can be treated the same as triples, or the GM can design their own ultra-extreme limiting method for each power source.

When mixing power sources, use the longest prep time and the most expensive ingredient costs, as well as any other limitations attached to any of the power sources.

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