This post is based on the analysis of the existing AGE spell and weapon mechanics (FAGE and DAGE). There are six elements of choice when creating a spell:
- Direct Effect
- Resist Chance
- Effect over Time
- Effect over Area
- TN or Target Number
The direct effect, resist chance and effect over time have a multiplicative relationship. The range and effect over area components are added on top. The total of these components create the raw MP value of the spell. The raw MP is then multiplied by the appropriate TN probability and an additional value of 4 is subtracted as action credit. The resulting value is rounded to create the final spell MP.
- Take the average of any dice roll as the value
- Any buff or debuff value is 1 to 1 with spell value
- Stunt point bonus are valued at 1 per SP
- Damage bonus, MP, HP, AR, focuses, ability scores also are valued at a 1 to 1 scale
- Penetrating damage is an extra 4 value
- Any resist chance can be applied as a 50% reduction of direct effect cost.
- If the effect is more complex with some remaining effect if the resist is successful, then you add together the direct value of both the success and fail cases and then apply the 50% reduction (like Flame Blast).
Effect Over Time
- The most effective rule I found for effects over time is to double the direct effect regardless of the length of time for the effect. When trying this rule on all the different duration conditions like rounds or minutes or hours, twice the single round cost is enough to capture an accurate valuation of the effect.
Effect Over Area
- I found a simple valuation for AOE component. The value of AOE is the number of affected squares minus 1 then divided by three.
- For a spell with a radius AOE description I found a formula that counts squares that works for any movement rules. The number of squares for a radius spell is 3*R2 + 3*R + 1. When using this with previous value formula it reduces to R2+R
- The value of range is 1 for every square (2 yards) in distance minus 1 (for the adjacent square)
TN Target Number
This one represent how easy it is to cast the spell. For zero ability character, a TN 11 spell has a 50% cast success chance, a TN 13 has a 25% cast success chance, etc. It is up to the designer to decide how hard to make this number. TN affects how much the spell will ultimately cost as well.
Putting It All Together - Lets pretend to invent the Firestorm spell using these simple formulas:
- Direct Effect - 3d6 damage + 2 for a failed dex test, total of 10.5+2, or 12.5
- Direct Effect - 3d6 damage + 0 for a successful dex test, total of 10.5
- Resist Chance - The two cases times 50% is (12.5+10.5)*0.5 is 11.5
- Effect Over Time - None
- Effect Over Area - 4 yard radius using the formula for counting squares is 22 + 2 is 6
- Range - spell has a 50 yard range or 25 squares. 25 - 1 is 24 value for range
- TN - firestorm should be a tricky spell so lets set it at a TN of 15.
Raw MP : 11.5 + 6+ 24 is 41.5
TN 15 chance is 9.26%. Times that by 41.5 gives you 3.84. Minus the 4 action credit puts the final spell cost at -0.16 MP. Now this is something you can measure the appropriateness of the TN value. We really don't want a free spell. Let's punch in different TN until we get something close to 11MP like in the book. TN 13 is the closest with 41.5*37.5% - 4 is 11.56 or 12 MP with rounding.
- Weapons are just simple spells with 1 range.
- Longsword - 2d6 or 7 Direct Effect. TN is 10. Final MP is 7*62.5%-4 is 0.375 or 0MP. The 0MP for weapons is really the minimum strength.
- 2H Axe - 3d6 or 10.5, TN10. 10.5*62.5%-4 is 2.56 or 3MP rounded (3 Min Str)
So that's how the system works so far. I have some ideas on how technology (like bows) would contribute to value through their cost in gold pieces.
PS - to look up what is the % for a TN, go to anydice.com punch in 3d6 to the calculator and look at the "At Least" table.