Quote:
Originally Posted by Asta Kask
I've been thinking about critical spell failure tables and want to toss out two ideas.
One is the idea of giving different traditions of mages different tables - this is implicit in the Dark Magic perk but this would apply to everyone.
The second idea is to vary table by area. So down in the valleys you have the standard table, but up on the faux-celtic Highlands you use another table.
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One thing you should seriously consider, if you do this, is to make critical failure tables that can take modifiers. The current ones, in GURPS Magic and GURPs Thaumatology, are 3d6-based with the worst outcomes occuring both on very low and very high rolls.
This means that there is no conceptual room to have any kind of effect, such as from an advantage or perk, or an enchantment, or a casting decision (such as to cast very slowly and carefully), that modifies the critical failure result roll.
And of course you can modify the probably too extreme mana level rules, which IIRC say that in a sufficiently high mana area, all casting failures are critical failures. Once you have a table that can take modifiers, the effect of mana above a certain level can simply be a +5 or +10 modifier to the table roll, so that on average the consequences are nastier.
Likewise, casting in too low mana can also have nastier consequences. Or you could have a separate table for too-low-mana that has consequences that are as nasty as the normal table, but they're all very subtle results, avoiding blatant observable consequence that threatens the low-mana ambience that you presumably want.
The only thing you can do is to allow X rolls, where X is 2 or 3 or in extreme cases 4, and then letting the player (or the GM, if it is an NPC casting) choose the preferred result, based on the assumption that the choice will tend strongly towards the less severe effects around the middle of the 3d6 table.
You could go with a 1d12 or 1d18 or 1d36 table, based on the assumption that you don't want to use dice with other than six sides, but keeping in mind that modifiers to such a table roll can be both positive and negative, you'd need to start the table at a negative value, e.g. -2 or -3, and end it at some point above the maximum roll outcome, e.g. 41 or 45 for an 1d36-based table.