Domibian Magic : d20 Style
NOTE: Much of the Domibian magic system is based on S
John Ross' wonderful Unlimited Mana system for GURPS.
Spell casting is not limited to a set number of spells of each level per day. All characters have a Threshold rating which is the limit that they can safely cast in a given time period. A spell costs an amount of Threshold equal to its level + one. Spells that are cast at a level higher than the caster's own must add the difference in levels to the cost. Spells that are "not in mind" also cost double to cast. Spells are considered "in mind" when they have been allocated for use in the standard fashion for that class. Improvised spells (see below) also cost double the normal cost. Note that all improvised spells will cost at least 4 times their level since they will never be "in mind". Do not use the standard D&D procedure for multiple doublings, instead use normal mathematical rules.
Ex: An "in mind" cantrip would cost 1 point (0+1). An improvised 9th level spell cast by a 3rd level wizard would cost 64 points (9+1+{9-3}*2*2).
Spell Fumble Table
Threshold
Threshold is calculated by adding up all the spells that a character can cast per day. Each spell is worth a number equal to its level +1. Thus 0 level spells are worth "1", 1st level spells are worth "2", 2nd level spells are worth "3" and so on. Clerics will have an additional amount of Threshold that can only be used for spells within their deity's domain. A spellcaster may also elect to take 1d6 subdual damage to generate one point of Threshold.
Ex: A 5th level sorcerer with a Charisma of 14 would have a Threshold of 35, six 0 level spells worth one each, seven 1st level spells worth 2 each and 5 2nd level spells worth 3 each; 6*(0+1)+7*(1+1)+5*(2+1)=35).
Recovery
Recovery occurs each day at a time specified by the player, in the same manner as a standard D&D spellcaster memorizes their daily spells or prays for clerical spells. Recovery is equal to Threshold / 4 (round up). Ex: The same sorcerer would have a Recovery of 9; Threshold 35 / 4 (round up).
Spell Failure
A roll must be made to successfully cast a spell. In general, a spell succeeds on any roll but a "1". This number is increased by one for each level that you lack to cast the spell in question and by two for each attribute level that you lack to cast the spell. If the roll is a failure a second roll must be made to determine the effect of the failure. Make an ability check with a DC = 10 + (spell's level - caster's level) + any levels of the Spellcraft skill. A success on this check means that the spell simply failed and cost no Threshold, a failure on this check means that the spell Critically failed and the Threshold was also spent. A Critical Failure must roll on the
Spell Fumble Table. A natural "1" on this roll is always a failure and a natural "20" is always a success.
Critical Success
A natural roll of "20" means a possible critical success. Make an ability check with a DC = 10 + (spell's level - caster's level) + any levels of the Spellcraft skill. A failure on this check means that the spell simply succeeded and cost normal Threshold, a success on this check means that the spell succeeded with no Threshold cost and at twice its normal effectiveness. A natural "1" on this roll is always a failure and a natural "20" is always a success.
Improvised Spellcasting
To cast an improvised spell takes an additional turn of concentration. At the end of the turn an ability check is made using the appropriate ability for that spellcaster. The DC is 20 + spell's level, the roll may be modified by ability bonuses and any levels of the Spellcraft skill. If this roll succeeds then an attempt may be made to cast the spell the following turn.
Exceeding Threshold
If Threshold is exceeded a roll must be made on the Calamity
table. A +1 modifier is added to this roll for every multiple of the caster's spellcasting level that has been exceeded.
New Feats
Improved Casting Ability: Adds +4 Threshold and +1 Recovery.
Improved Improvised Spellcasting: Adds +2 to checks to improvise spells.
Improved Recovery: Adds +2 Recovery.
Improved Threshold: Adds +8 Threshold.
Aspected Mana
Locations can become aspected to a particular "domain", which helps or hinders spellcasting depending on the spell's nature. A location that became death aspected would give a positive bonus to cast death-oriented spells and a negative penalty to cast healing oriented spells. The size of the modifier is based on the strength of the aspect. Usually the maximum for an area almost dripping with the elements of that domain would be +4, with most aspected areas being a simple +1.