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Calculate in Advanced Dungeons & Dragons

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Calculate

Name
Calculate
Type of Magic
Priest
Spell Level
1st
School
Greater and Lesser Divination (House Sextus)
Sphere
Numbers
Reversible?
No
Range
​0​
Components

Material, Somatic

The material component for this spell is a miniature abacus of ivory worth at least 100 gp. It is not consumed in the casting of the spell.

Duration
​Instantaneous
Casting Time
​4​
Area of Effect
​The caster
Saving Throw
None
Effects
​By means of this spell, the priest can accurately estimate the chance of success of one specific action, such as climbing a dangerous cliff, making a trick bowshot, crossing a burning room unharmed, or even striking an enemy. The action in question must be one that would normally be resolved by a die roll, but the priest doesn’t have to be the person who attempts the feat; he can use Calculate to estimate the odds for anyone taking an action in his sight. The priest has a 70% chance, +2% per level, of making an accurate estimate.​ ​If successful, the DM reveals to the player the action’s chance for success or any modifiers that may be in play. For example, he could reveal a particular opponent’s Armor Class or THAC0, the saving throw an opponent would require in order to save against a particular spell cast by the priest or the priest’s wizard companion, or a character’s chance to open doors, bend bars, or use a thief ability. The priest could even Calculate his odds for actions that might be resolved by a die roll or DM caprice, such as his chance to avoid detection by hiding behind a rock. This spell takes into account factors that the priest himself may not be aware of, so from time to time a character may receive some very confusing results from this spell. For instance, if the priest doesn’t know that an orc chieftain is actually a polymorphed tanar’ri masquerading as an orc, he may be astonished to learn that the “orc” has a THAC0 of 7!​ ​If the priest fails his calculation check with a roll of 99 or 00, his calculation is wildly skewed in a random fashion. ​
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