Considering we saw that directly, Nirvana gives +57 acc and attack (when combined with seraphicaller), i'd assume a similar bonus to magic accuracy and attack. i'd wager a viable way to test would be to do nirvana+seraphicaller vs seraphicaller+caller's doublet2+spurrina gages+ngen and seeing how much of a damage difference like.. netherblast does.
seraphicaller: 1285
seraphicaller+20% in gear: 1542
seraphicaller+nirvana: 1871
Increase of 72 damage over what +40% ~should~ be, which is 1799
pulling out the 40% damage bonus (from the 1871), it's a damage difference of +51 damage over base 1285.
This was simply done on a single mandy outside of western adoulin.
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