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Monday, May 18, 2020

Emergency Spell Casting

A recent conversation on Twitter got me thinking again about casting spells from spell books. Some people treat spell books as big, expensive magic scrolls, allowing casters to cast spells from them, but with the spell disappearing from the book when cast. I don’t treat them that way. I won’t go into all the details, because it’s something I’ve talked about many times.

But… I do like the idea of casting spells with spell books, an emergency spell-casting procedure that takes longer than a normal prepped spell to cast. Only spells the caster knows and could prep for casting can be cast this way. Here is my current thinking on rules for handling this.

Step I: Ingredients

If spell prep for spells in your campaign involves burning things, pouring libations, ritual sacrifices, or any other physical components, the caster needs to have these handy, or scavenge around for them. The easiest way to handle this, to me, would be to set a monetary value of ingredients needed and materials available. For example, spells might require 20 coins worth of common ingredients per spell level, and casters can spend a turn in any non-empty room to scavenge: roll 1d6, 5+ means 20 coins value has been found, otherwise add 1 to result for number of coins worth found. Inhabited rooms might double or triple the value found, magic labs will multiply by 10.

Step II: Casting Time

GM rolls casting time in secret: 1d6 x Spell Level, in turns. Players say how long they chant and perform rituals. If they don’t meet the necessary time, the spell is a miscast If they meet or exceed it, it is a success.

Step III: Spell Effect

GM makes a reaction roll: 2d6 on Spell Effect Table for a successful cast, but only 1d6 for a miscast. If the caster would not be able to prep the spell (in other words, doesn’t have an empty spell slot for the spell being cast,) shift the result up one line, making the spell effect one category worse. A blessed caster shifts the result down one line, making the spell effect one category better.

2d6 Roll Effect Detailed Explanation
0 Major Backfire Random spell and random target.
1 Backfire Random target, benefits are reversed.
2 Minor Backfire Random target.
3-5 Fizzle Half normal strength.
6-8 Weak 1 point weaker.
9-11 Normal Standard spell effect.
12 Strong 1 point better.
13+ Fantastic Double normal strength.

I’ve talked before about randomizing spell targets: everyone rolls a d6, and the GM rolls a d6 for the spell. Anyone whose roll matches the spell’s roll is affected. On this table, a major backfire randomizes the spell as well; easiest way to do this is to roll 2d6 and subtract 7 from the result, then count backwards or forwards on the list of spells to get the replacement.

A fizzled spell does half damage, lasts half as long, travels half as far, and is otherwise half strength in every way. A fantastic spell effect is the opposite, doubling strength in every way. A weak or strong spell decreases or increases damage, duration, distance, and so on by a tiny degree, but never as low as half the minimum or more than the 1.5 x maximum effect.

Notes on Time and Cost

Time above is given in turns, so that whether you use ten-minute turns, one-minute-turns, or something else, the rules will automatically scale to whatever you use… as long as normally a prepared spell requires one turn or less to cast. If you have adjusted either casting time or prep time so that it is not based on this assumption, you may have to throw in an extra multiplier to make sure emergency casting takes longer than standard spell casting or spell prep.

Costs are given in coins, which will be copper, silver, or gold, depending on whatever standard you are using for common equipment prices in your campaign. The assumption is that “material components” are used during spell prep, but not spell casting, and most spells have unnamed commonly available components.

If some spell levels have much higher ingredient costs, you can add a multiplier for different spell level ranges, for example:
  • Spell Levels 1-3: Standard cost (20 coins per level)
  • Spell Levels 4-6: High cost (100 coins per level)
  • Spell Levels 7-9: Very High cost (500 coins per level)
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