Advanced d20 Magic » Casting DC


In dynamic casting systems, the key measure of a spell's power is not spell level, as it is in the core rules, but rather the DC of the Fortitude Save required to cast the spell.
For standard spells, the DC is listed in the spell description, otherwise the spell must be converted for use to establish its DC.

[top]Fortitude Saves

Spellcasting Fortitude Saves
Check ResultEffect
Pass by 10 or more1/2 base Drain,
(round up) no Control check
Pass by less than 10Base Drain,
no Control check
Fail by less than 10Double base Drain,
Control check required
Fail by 10 or moreDouble base Drain,
Control check required
spellcaster fatigued
A spellcaster must make a Fortitude Save whenever they cast a spell based on the casting DC of the spell. The results of the check can be determined by consulting the Fortitude Saves table on the right.


Table 1: Spell Base DC
Spell LevelBase DCSpell LevelBase DC
To determine the DC when converting a spell,
  • Establish the spell's base DC, according to table 1: Spell Based DC.
  • Adjust the base DC for casting time (or form used)
  • Apply focus modifiers
  • Apply modifiers for xp investment
  • Based on comparison to existing spells, adjust the final DC to represent the difficulty or power of the spell, as appropriate.

Table 2: Spellcasting Priority
Sorcerer or WizardHighest
Ranger or Paladin
Domain Spell
Prestige ClassLowest
The base DC for a spell is determined by the spell's level. The base DC's for spells of level 0 to 9 are listed on Table 1. Some spells are listed at different levels for different spellcasting classes. When spells are listed with multiple class and
Level combinations, use the first spellcasting Class Level given for that spell on Table 2: Spellcasting Priority. Go down the list and take the Level of the first class that may cast the spell. That is, a spell available to both sorcerers and bards should use the spell Level for the sorcerer/wizard class. Alternatively, if a spell lists two different Levels for druids and rangers, use the Level indicated for the druid (the first class able to cast the spell on Table 2).

[top]Form and Casting Time

In this system, the basic unit of casting time is 1 action. This is used for all spells, regardless of origin. After conversion, every spell will have a base casting time of 1 action.
Many spells to be converted are originally listed with longer casting times. To accommodate this, the casting DCs for more
complex spells (as noted by the additional time needed to cast them under the standard d20 rules) are increased if their casting times were originally longer than 1 action.
Symbol of death has a normal casting time of 10 minutes. What this means is that casting symbol of death in 10 minutes is about as difficult as casting any other 8th-Level spell (normally a DC 48). To properly adjust the spell?s DC, the bonus for a 10-minute casting time (+10) is added to the base DC to determine the difficulty of casting the spell in one action, for a total DC of 58.
Using this system, spells are designed to fly thick and fast. Spellcasting can be done with the wave of a hand if you?re skilled enough, even with difficult spells. Of course, taking time helps to insure better results, but that choice is left to the caster to make, not decided for him or her. Instead, the casting time is interpreted as using ritual to lengthen the time needed to cast the spell and make it easier for the caster to focus the magical energies of the spell. The final version of the converted spell should have the DC listed for casting it in a single round.
Spells should not assume the use of either Invocation or Incantation. A spell that is listed as requiring 1 round to cast is not considered to be using an Incantation; rather it assumes the caster is using a +1 round Ritual form (+1 bonus). The reason for this is that the use of Invocation makes it obvious what spell is being cast -- an option spellcasters should not be forced into taking. Incantation is similarly a very identifiable way of casting a spell, and is therefore also left as a matter of choice.
Remember that when casting a spell with a +1-round ritual but not using Incantation, the spell takes only one round to cast (though it takes the full round instead of a single action). When using both Incantation and a +1-round ritual, the spell requires 2 rounds to cast, etc.
Complete conversion by determing the number of spell slots required to learn the spell, and recalculating the save DC of the spell.

[top]Focus Modifiers

Many spells do not require a material component in order to cast them. Those that do, however, are considered under these rules to use a focus. A focus can be any material item required to cast a spell. Foci can be either a basic focus (a holy symbol) or an expendable focus (material components). Where the preconversion spell assumes the use of one of these types of foci in a spell, the converted spell has an increased DC (representing the cost to cast the spell without the focus).
The caster can ultimately decide to cast the spell with a focus (or Ritual, or Incantation, or Investment) or without. A spell cast without the focus uses the base DC with no bonus to casting rolls. Should the spellcaster opt to use a focus, he or she gains a bonus on spellcasting rolls for that spell. A basic spell focus increases the DC by +2. An expendable
focus increases the DC by an amount as the bonus normally provided by that focus.


Very powerful spells sometimes require the expenditure of experience points or hit points in order to cast them. In Advanced d20 Magic, these requirements are removed from the spell when it is converted, leaving the decision to use such investment in the hands of the character when the spell is cast. The DC is adjusted accordingly, however, to note the additional difficulty that a spell of that magnitude will naturally entail. For a spell that originally required the character to expend XP, increase the DC by +1 per 100 XP required in the spell description. It is possible to cast these spells without expending experience, but it becomes much more difficult.

[top]Final Adjustmets

Once the final DC of the spell is determined, it should be adjusted if it seems too high or too low. Compare the spell against others of similar DC to see if it seems too effective or not effective enough to be balanced with these other spells. The GM will have to make the final determination about any DC adjustments. Remember that while the goal of this system is flexibility in magic, some spells will simply require more time and energy to successfully cast than others will.

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